Zuckerberg loses $2 billion on second day of Facebook trading Facebook CEO Mark Zuckerberg and his then-girlfriend Priscilla Chan walk in downtown Shanghai. Young Yee / European Pressphoto Agency May 21, 2012, 1:44 p.m. For Mark Zuckerberg's sake, hopefully he went on a honeymoon because he'll need something to take his mind off the billions of dollars he lost on Facebook's second day of trading. Zuckerberg had a pretty good week for a 28-year-old last week. He ended Friday with his Facebook holdings valued at more than $19 billion, and he followed that up with a surprise wedding, marrying his longtime girlfriend at his place in Palo Alto. But this week has not gotten off to a good start for Facebook and its CEO. Shares of the social network began to trade under its $38 IPO price for the first time on its second day in the public market. Facebook shares opened Monday at $35.75, and at one point they went down as low as $33. Zuckerberg, who owns 503.6 million shares of his company, saw the value of the Facebook shares he holds slide from $19.25 billion at the end of the day Friday to $18 billion at the start of regular trading Monday and then all the way down to about $16.62 billion. After the substantial dip, Facebook shares moved up a little, but never quite made it near its IPO price Monday. At the close of the trading day, Facebook had a stock price of $34.03, down almost 11% from its close Friday. At that price, Zuckerberg's Facebook holdings are worth about $17.14 billion. That's a loss of about $2.11 billion.