And, it's off! 
 
 Groupon priced its IPO last night at $20 a share and started trading this morning around $30. 
 
 So, it's already been a hell of a ride. 
 
 Right now, the big institutional investors who got the stock at $20 and swore up and down that they'd hold it forever are now gleefully flipping it to anyone who will buy it. 
 
 And if I were a big institutional investor, I'd be doing exactly the same thing. 
 
 There is NO WAY I would own Groupon's stock for the next few quarters at this price, given the business transition Groupon is currently undergoing. 
 
 At ~$30 a share, Groupon's valuation is about $20 billion. If the next few quarters are as rough as I think they might be, the stock could easily trade down to ~$8 billion, or ~$12 a share. That's a long way down from here. 
 
 Groupon's near-term upside, meanwhile, appears to be limited, at least based on the company's fundamentals. Groupon is already being valued at a fifth of Amazon's value. It has already picked the low-hanging fruit in its key markets. It is cutting back on marketing costs, which is bringing growth to a screeching halt. Its core business in the US is shrinking. And Groupon is already totally global--there aren't many new markets to roll out in. 
 
 Long-term, I'm actually a Groupon bull. I think the company has discovered a huge new market, and its scale gives it a big barrier to entry. But that doesn't mean the ride will be smooth. 
 
 Could Groupon, say, double from here over the next 6 months and never trade below this level again? 
 
 Sure, it could. Anything's possible. But that doesn't seem likely. And, in any case, the risk/reward profile of 100% upside (25% probability) and ~75% downside just doesn't seem that compelling. 
 
 So, enjoy the ride, Groupon shareholders! I'll be watching the next act from the sidelines. 
 
 WHY COULD THE STOCK GET CRUSHED OVER THE NEXT FEW QUARTERS? 
 
 Over short-term time frames, two factors drive stock prices: 
 
 Some market observers like to pretend that all stocks have a precise value that analysts can determine by studying the company and then running the right numbers. 
 
 This is a crock. 
 
 The theoretical value of any stock is the "present value of future cash flows." And that means that, to estimate the intrinsic value of the stock, you have to know two things: 
 
 The future cash flows 
 
 The rate at which to discount the cash flows to get a "present value." 
 
 Regardless of what you may think from watching financial TV, no one knows either of these things. And how could they? We have no idea what Groupon's cash flow will be this quarter, let alone two years from now or 10 years from now or 50 years from now, all of which count in the "present value" calculation. We also don't know what the "right" discount rate is. And adjusting the discount rate by even a percentage point or two makes a huge difference in the present value calculation. 
 
 So don't believe anyone who tells you they know what Groupon's worth. They don't. All they know is what their estimate is of what Groupon is worth. And, unfortunately, the range of "reasonable" estimates of what Groupon (or any stock) is worth is wide enough to fly a 787 through. 
 
 But still, we have to try. 
 
 So let's start with the big picture. 
 
 The big picture is this: 
 
 Groupon generated ~$300 million of revenue last year and should generate about $1.7 billion of revenue this year . 
 
 . Groupon is now operating basically at break-even , with the North American business earning a modest profit and the international business losing a modest amount. 
 
 , with the North American business earning a modest profit and the international business losing a modest amount. Groupon is cash-flow positive and has ~$1 billion in the bank 
 
 Groupon's growth rate is decelerating sharply, and this deceleration is likely to continue for at least several more quarters. 
 
 Based on my experience (15 or so years of following tech stocks), that last factor is very important. "Momentum" investors HATE deceleration. And momentum investors have a big impact on the prices at which stocks trade. So we need to keep the deceleration in mind. 
 
 In fact, let's start with the deceleration, because it will have a big impact on our fundamental estimates for the next couple of years. 
 
 The reason Groupon's growth is decelerating is: 
 
 the law of large numbers — the company's already huge, and the company is cutting back on marketing spending 
 
 The second factor is very important. To become meaningfully profitable, Groupon will have to continue to clamp down on marketing. And this will likely lead to further deceleration. 
 
 Here's a chart from Yipit that shows Groupon's deceleration. Growth is screeching to a halt: 
 
 Yipit 
 
 There may be another factor at work in the deceleration, which is "daily deal fatigue," as the novelty of Groupon's offering wears off. We need to keep that one in mind, too. 
 
 WARNING: Deceleration Can Be Hazardous To Your Wealth 
 
 Now, in my experience, when companies decide to transition from hyper-growth-and-losses to sustainable-growth-and-profitability, as Groupon is, the transition can be very rough. 
 
 Importantly for this exercise, it also can be absolute hell on stock prices. 
 
 The example that jumps to mind is Amazon.com. 
 
 From 1996-2000, Amazon grew like a bat out of hell, in part because it was spending boatloads of money on marketing. In 2000, however, the funding markets for unprofitable Internet companies dried up, and Amazon had to change tack and focus on becoming profitable. This transition took two years, from 2000-2002. It led to major deceleration in the business. And it was absolutely brutal on Amazon's stock price. 
 
 Specifically, as Amazon cut back on marketing spending and other profligate expenses in its drive to become profitable, the stock collapsed more than 95%, from $100+ to, if memory serves, about $6 a share. See the right half of the chart below. 
 
 The painful transition from growth to profits: Amazon's stock price, 1997-2001. Google Finance 
 
 Importantly, through this period, Amazon kept growing. It's just that its growth rate slowed sharply. 
 
 During this period, Amazon also had some problems that Groupon probably won't, which is that many investors were convinced it could "never make money" and was going to "go bankrupt." Groupon's most recent quarter should have helped put these concerns about Groupon to rest. 
 
 But Groupon's deceleration is a big issue for the stock price. Such a big issue, in fact, that I personally would not even consider buying the stock unless/until one of two things happened: 
 
 The growth rate stabilized 
 
 The stock price was so low that I felt like my downside was limited regardless of what happened to the growth rate. 
 
 So where will Groupon's growth rate stabilize? 
 
 One could certainly make the case that Groupon's growth rate will eventually go negative — the company will begin to shrink — because management will be forced to cut back so sharply on marketing costs. 
 
 I think that's probably too negative a scenario. Groupon already has a huge base of email subscribers — 150 million — that it can market to for free. And the company should also be able to continue to spend $150+ million per quarter on marketing. And when revenue grows, the company should be able to increase this spending. 
 
 So I think it's reasonable to assume that Groupon's growth rate will settle in the mid single-digits (sequential), which might translate to 20%-30% year-over-year growth. 
 
 That transition will probably take a couple of quarters to play out. 
 
 One, Two, Three ... Estimate! 
 
 So now let's sketch out some numbers. 
 
 If Groupon ends this year with a $500 million quarter, it will be operating at a $2 billion revenue run-rate. If the company can grow 20%+ next year off this run-rate, it would post 2012 revenue of ~$2.5 billion. And if it can grow another 20% in 2013, it will post 2013 revenue of about $3 billion. 
 
 And what about profits? 
 
 I realize I'm probably in the minority here, but I think Groupon will eventually have a nicely profitable business. The North American business had a 12% operating profit margin in Q3, and I think there's probably upside from there (there's also plenty of downside, obviously). 
 
 International will likely drag the company's overall margin down for some time. But I think it's reasonable to assume that Groupon might generate a 10% operating profit margin in 2012 and a 15% operating margin in 2013. 
 
 So what does that give us for preliminary estimates? 
 
 2012 Revenue: ~$2.5 billion Operating Profit (assuming 10% margin): $250 million Net Income (assuming 35% tax rate): ~$150 million 
 
 2013 Revenue: ~$3 billion Operating Profit (assuming 15% margin): ~$450 million Net Income (assuming 35% tax rate): ~$300 million 
 
 So what might the stock be "worth" on those estimates? 
 
 A fast-growing market-leader with a huge global opportunity should eventually trade at 20X-30X earnings. More in the early years, when the growth rate is faster and the company has not yet achieved its steady-state profit margin, less in the later years. 
 
 So if Groupon were to trade at, say, 20X-30X 2013 earnings of $300 million, it would trade in a valuation range of $6 billion to $9 billion, with a central value of $7.5 billion. This would equate to a range of about $9-$13 per share. 
 
 Notably, that's well below where the stock is trading. 
 
 So ... Groupon Already Looks Overvalued 
 
 Could Groupon do much better than that scenario? 
 
 Of course it could. 
 
 Its growth rate could stabilize at, say, 40%, and it could become much more profitable than I currently think. 
 
 Goldman Sachs, who helped take the company public, thinks Groupon's revenue will grow at 40% for the next two years and that the company will have a 30% profit margin in 2013. Goldman thinks this will enable Groupon to earn almost $1 a share in 2013. If Groupon actually hits those numbers, or exceeds them, the stock's current valuation looks more reasonable. 
 
 Of course, Groupon could also do much worse than my scenario. 
 
 Namely, it could stop growing, and, thanks to competition or pushback from merchants, it could have a much lower profit margin than I think. And it could therefore be worth much less than the $6-$9 billion range I laid out. 
 
 I think there's as much chance that the negative-case scenario will play out over the next couple of years than the positive-case one. So I would only consider buying the stock at a discount to "base case" scenario I outlined above. 
 
 So, What's Groupon Worth? 
 
 So what might I be willing to pay for Groupon's stock? 
 
 Right now, based on the information I have and the assumptions I've made above, I wouldn't buy Groupon's stock unless it were trading at or below $5 billion (~$7 a share). This is in part because of the "deceleration" pattern I described above and in part because of the high level of riskiness I think goes along with owning the stock. 
 
 So if I were managing a big institutional fund, here's what I would do: 
 
 I'd have placed an order on the IPO for 1 million shares 
 
 I'd have gotten my allocation of, say, 200,000 shares 
 
 I'd have already flipped the stock to other investors 
 
 (It's great to be a big institutional investor.) 
 
 Then I would sit on the sidelines and watch Groupon and Groupon's stock for a couple of quarters. 
 
 And if Groupon's growth rate stabilized at 40%-50%, I'd say, "you dope — you missed a big opportunity." 
 
 And if Groupon's growth rate stabilized where I thought it would or below, I'd say, "Glad we dodged that bullet." 
 
 And, of course, as time went by, I'd keep running new estimates, which I would compare to Groupon's stock price. And if the stock price ever dropped to a level relative to those estimates in which I thought I had a nice margin of safety in buying the stock, I'd buy it. 
 
 After all, Groupon does seem to have identified a massive new e-commerce opportunity, and I'd like to go along for that ride. 
 
 But that's me. And it's not a stock recommendation. I have no idea what your particular circumstances and investment goals are, and I couldn't care less whether or not you buy the stock. 
 
 (And I should add here that, for me, at least, this exercise is totally academic. I don't buy individual stocks. I don't buy them because, having been a Wall Street insider for a decade, I learned firsthand just how much of a disadvantage most outsiders are at. I also learned that even the smartest, best-informed insiders are wrong about 50% of the time. And I learned that, beyond a shadow of a doubt, the most intelligent investment strategy for part-time investors not paid to manage someone else's money is to assemble a diversified portfolio of low-cost index funds. And that's what I've done for myself. So, beyond the entertainment value, I really couldn't care less what Groupon's stock does.) 
 
 SEE ALSO: Congratulations, Groupon! ||||| Getty Images 
 
 Holy stock pop. 
 
 In its first minutes as a public company, Groupon’s stock soared about 40% from its $20-a-share IPO price. 
 
 Groupon shares in morning trading bumped around, trading as high as 56% above the IPO price. UPDATE: Groupon shares ended the first day of trading at $26.11, up 31% from the IPO price. 
 
 The three-year-old company with a long line of critics, debuted as a public company last night with a market value of $12.7 billion — more than Xerox, Research in Motion or The Gap. Right now, Groupon’s market value is $16.5 billion. 
 
 Yes, that’s right. The Wall Street bankers may have rigged this IPO baby juuust right. But while the stock surge makes the Groupon IPO look like the greatest thing since sliced bread, there are a couple of huge caution flags. 
 
 First, this stock increase means the privileged investors who landed Groupon IPO shares now are flipping their stock for a quick profit. That’s not a great sign (even though it happens all the time). 
 
 And second, Groupon has sold only a teeny slice of the company to the public — less than 6%. That means the stock price is going to be very, very bumpy, maybe even today. 
 
 READ MORE ABOUT THE GROUPON IPO: 
 
 * Meet the Groupon IPO Millionaires (and Billionaires) 
 
 * Groupon: Officially the Biggest Internet IPO Since Google 
 
 * Groupon’s Stock Pop Is Pathetic by Dotcom Standards (And That’s a Good Thing.) 
 
 * Groupon Who? Today’s “Other” IPO 
 
 * Former IPO Stars: Where Are They Now?
– Groupon is having a big debut as a public company. The stock was selling for about $30 a share at the market's open today, way above the $20 IPO price the company set last night, reports the Wall Street Journal. Which means that, on paper anyway, the company is valued at about $20 billion. Part of the surge: Institutional investors who got the stock early are flipping it for profit just as fast as they can, notes Henry Blodget at Business Insider. You won't catch him on the bandwagon: "There is NO WAY I would own Groupon's stock for the next few quarters at this price, given the business transition Groupon is currently undergoing," he writes. Sure, it's possible the stock might double, but from the looks of things, it could easily drop to $12 a share in the near future.