Facebook Files for an I.P.O. It sure pays to have friends. Facebook, the vast online social network, took its first step toward becoming a publicly traded company on Wednesday as it filed to sell shares on the stock market. The service, hatched in a Harvard dormitory room nearly eight years ago, is on track to be the largest Internet initial public offering ever - trumping Google's in 2004 or Netscape's nearly a decade before that. In its filing, Facebook, which has more than 845 million users worldwide, said it was seeking to raise $5 billion, according to a figure used to calculate the registration fee. The company will seek to have the ticker "FB" for its shares, but did not list an exchange. But many close to the company say that Facebook is aiming for a far greater offering that could value it as high as $75 billion to $100 billion. At that lofty valuation, Facebook would be much bigger than many longer-established American companies, including Abbott Laboratories, Caterpillar, Kraft Foods, Goldman Sachs and Ford Motor. "Facebook's I.P.O. marks another stage of the Internet's evolution," said Charlene Yi, founder of the Altimeter Group, a technology consulting firm. It's so valuable, because it's not just about content, it's about our connections. The filing sheds some light on how its meteoric run has turned the upstart into a formidable money maker. The company, which makes the bulk of its money from advertising and the sale of virtual goods, recorded revenue of $3.7 billion last year, an 88 percent increase from the prior year. During that period, Facebook posted a profit of $1 billion. It is still a fraction of the size of its rival Google, which recorded revenue of $37.9 billion last year, but many analysts believe Facebook's fortunes will rapidly multiply as advertisers direct more and more capital to the Web's social hive. Facebook, unlike any other site, has come to define the social era of the Web. More than a portal, its value lies in its dynamic network of social connections and the enormous amount of information shared by its users. In many ways, Facebook is a data processor, archiving and analyzing every shred of information, including its users" interests, locations and every article and link that they "like." The collection of data is a potential goldmine for advertisers, keen to better understand and target consumers. "Facebook changed the way entrepreneurs thought about platforms and sharing," said Shervin Pishevar, a Menlo Ventures partner who built games on Facebook as the former chief of the Social Gaming Network. Indeed, the social network has become something like an economy into itself, fostering businesses like the music service Spotify. The game maker Zynga, which went public late last year, generates more than 90 percent of its sales from Facebook. "Facebook has become the biggest distribution platform on the Web," said Daniel Ek, the founder of Spotify, a service that accepts only Facebook users. We noticed that users who connected our service to Facebook were three times more likely to become a paying user. But for all the promise of Facebook, the company is still trying to figure out how to properly extract and leverage data while keeping its ecosystem intact. For all its billions, Facebook makes a small sum on a per-user basis. Last year, it made a little more than $1 per user. The Wall Street firms underwriting the I.P.O. are Morgan Stanley, JPMorgan Chase, Goldman Sachs, Bank of America-Merrill Lynch, Barclays Capital and Allen & Company. Facebook has come a long way from its scrappy start-up days. Mr. Zuckerberg, a freckle-faced computer prodigy from Dobbs Ferry, N.Y., started the service, then known as Thefacebook, in his Harvard dorm room in February of 2004. He rolled out the site carefully, first opening it up to other Ivy League schools to keep the community intimate. Some of Mr. Zuckerberg's classmates sent e-mails to old high school friends, cajoling them to join the site. By the end of 2004, the site reached one million users. "That's the kind of stuff I do - small little projects, and eventually they all fit together," a young Mr. Zuckerberg told The Harvard Crimson. Like Google, Facebook was not the first in its category. Start-ups like Six Degrees.com, Myspace, LinkedIn, Friendster and others predated the service. But Facebook quickly eclipsed the competition by drilling down on the mechanics of sharing. In 2006, Facebook made it easier for users to keep tabs on their connections by introducing news feeds. These data streams made sharing automatic, broadcasting short bursts of information, updates and announcements, from friends in real time. One year later, Mr. Zuckerberg rolled out the Facebook Platform. The move effectively collapsed the walls that separated the service from the rest of the Web by allowing third parties to develop applications on the site. The policy of openness and Facebook's pursuit of so-called "frictionless sharing" has made it nearly impossible to escape its long shadow online. Over the last four years, its user base has grown to 845 million from roughly 50 million. On average, users spend more than 9.7 billion minutes a day on the site, according to the filing. Mr. Zuckerberg has been made wealthy by Facebook, and an I.P.O. would make him wealthier. When Facebook was valued at $23 billion, Forbes magazine estimated his wealth at $6.9 billion. At a market value of $100 billion, Mr. Zuckerberg's 28.4 percent stake in Facebook would be worth $28.4 billion. Yet his ambitions seem more akin to Alexander Graham Bell than to other Internet billionaires. Mr. Zuckerberg says he wants to "make the world a more open place," according to his Facebook profile. In recent months, his team has rolled out more features toward that end, like Timeline, which makes it easy to scroll through a user's entire history, and new partnerships, with companies like Ticketmaster, that will allow users to pull even more data from outside publishers into Facebook's platform. The company is also said to be designing its own mobile phone, which will give Facebook an even larger footprint in its users" digital lives. Mr. Zuckerberg's push for openness has not always been embraced by the online community, which, at times, has been leery of his efforts to reset the boundaries of what people should share. Facebook, as the protector and transmitter of personal information, has to maintain a delicate balance between financial interests and the privacy concerns of its users. Major changes to Facebook's platform have frequently inspired fierce backlashes, including calls to boycott, lawsuits and the ire of lawmakers. As Facebook's influence grows, so too does scrutiny from Washington. In November, Facebook reached a settlement with the Federal Trade Commission, after the regulators accused the social network of misleading customers on privacy issues. With sharing at the center of Facebook, and the new Web, analysts also wonder whether the constant chatter will create too much white noise. As psychological barriers to sharing fall and companies become more deft at leveraging social media, there's a legitimate concern that platforms, like Facebook, will be less valuable without the proper filters. And user growth has slowed in some mature markets. In the United States and Canada, the company added three million users - for a total of 179 million - in the fourth quarter of 2011. In the previous quarter, Facebook had added seven million users. What are the limits of sharing? Ms. Yi, of the Altimeter Group, said. At what point does the presence of all these partners on Facebook, all this sharing, begin to degrade the quality of the site overall?