HispanicBusiness

"It's unusual, but I think people are convinced that Mark has been a terrifically effective and inspiring leader," the investor said, who spoke on condition of anonymity because of federal regulations. "There were no concerns that he was able to do the job. He's been so right, and he's been singularly focused on the product. We saw the potential as unlimited."

Facebook first turned a profit in 2009, when it earned $229 million on $777 million in sales, according to the filing. And the company is not hurting for cash. At the end of 2011, Facebook had $3.9 billion in cash and marketable securities, up from $1.8 billion at the end of 2010.

The bulk of Facebook's revenue -- 85 percent -- comes from advertising, but a growing portion of it comes from fees through "Facebook Credits," largely those related to processing payments for virtual and other goods purchased on the site.

Despite the strong revenue numbers, there were also some signs in the Facebook filing that could be a potential concern for investors.

"I don't think anyone would say this isn't an extraordinary business, but it's also probably going to be valued like one that will do phenomenal things for a long time," said Joe Magyer, a senior analyst with the Motley Fool. "If they fall anywhere short of sustained awesomeness, the stock is going to disappoint."

Facebook has seen its user base grow phenomenally over time, but Wednesday's filing indicates that its user growth has slowed markedly, and Facebook said it would have to concentrate on developing nations outside Europe and North America to expand its membership in the future. That means Facebook will need to find ways to get users to spend more and more time on the social network, increasing revenue by exposing them to more advertising.

And while about 425 million people use Facebook on a mobile device each month, the company highlighted the move to the mobile Web as a substantial risk. Facebook generates virtually no revenue from mobile now, and mobile ads are less lucrative per ad than desktop ads. Meanwhile, rivals Google and Apple (AAPL) control the mobile software platforms most smartphone users rely on to access the social network.

"That's the No. 1 risk to the Facebook story, in my mind," said Lou Kerner, an analyst with Liquidnet. Internet "use has migrated to mobile and they are not monetizing it."

Only a handful of companies worldwide have debuted on the public market with total market capitalization of $70 billion or more, according to research firm Dealogic. None of them were U.S. or tech companies.

If expectations for the value of Facebook's IPO prove true, the company would be worth far more, for example, than Hewlett-Packard's (HPQ) market value of $55.5 billion. Google, by comparison, has a market capitalization of more than $188 billion, while Apple is worth more than $425 billion.

Facebook is much smaller than those companies, in both revenue and workforce. But it has been on a rapid growth curve.

The number of Facebook employees increased by 50 percent last year, as the company ended the year with 3,200 employees -- including those at the company's new headquarters on the former Sun Microsystems campus in Menlo Park, the company revealed in Wednesday's filing.

Over the next month, the Securities and Exchange Commission will scrutinize Facebook's filing, before the company begins a series of presentations to potential investors. Trading of Facebook stock, under the symbol "FB," might start somewhere toward the middle of the year. Facebook has not yet decided on which stock exchange it will trade.

And while the atmosphere at Facebook's Menlo Park campus was very much business as usual Wednesday, with no signs of popping champagne corks or spontaneous celebrations of any kind, some large investors were preparing to celebrate.

"It's a tectonic shift in the history of capitalism," said Manuel Henriquez, CEO of Palo Alto-based investment fund Hercules Technology Growth Capital, which last month bought 300,000 shares of Facebook on the secondary markets for $10 million. "A college dropout, 27 years old, brings Wall Street to its knees."

Staff writer Joshua Melvin contributed to this report. Contact Mike Swift at 408-271-3648.

The 3 Big surprises

Facebook's IPO filing was chock full of unexpected tidbits. Here are our top picks. CEO Mark Zuckerberg controls 57.1 percent of the voting power among Facebook shareholders, giving him the final say on company decisions. One company -- social game provider Zynga --contributes 12 percent of Facebook's total revenue and the majority of its fast-growing payments business. Facebook posted $1 billion in profit last year, making it one of the Valley's most profitable tech companies.