Facebook Files for $5 Billion IPO: FB Should Trade This Spring

As expected, Facebook just filed its $5 billion mega-IPO. We're sorting through the details now, but some important stats already stand out: 845 million users, 100 billion friendships, and a whole lot of money heading Zuck's way. Stock market, meet FB.

Of those 845 million users, 483 million were active on a day to day basis, an impressive level of engagement (especially compared to how many inactive users other social media sites like Twitter is burdened with). The company also took in 3.7 billion in revenue last year. That's chump change compared to the likes of Apple and Google—and means Facebook has a long way to go to live up to its valuation—but the fact that the company is able to make even that much money through dinky sidebar ads is a feat in and of itself.

Not that Facebook makes all of its money off of tooth whitening offers; a whopping 12% of the money the company in came from Zynga, and presumably not because of a few well-timed Farmville trades. To lean so heavily on one source for incoming money could be daunting for potential investors—particularly when that source could easily turn out to be a fad.

That's not the only rocky road ahead. As part of its filing, Facebook is required to disclose possible pitfalls ahead for the company. And there are a lot of them, starting with, curiously, mobile:

We do not currently directly generate any meaningful revenue from the use of Facebook mobile products, and our ability to do so successfully is unproven.

There's no elegant way to serve you ads when you check your news feed through a Facebook app or a mobile browser. Which means it's terribly difficult for Facebook to make money during that time.

Most of all, what emerges is the portrait of a platform that, despite its global prominence and ubiquity, hasn't yet come into its own as a business. And to date, it hasn't had to. The company made a billion dollars in profit last year, nearly twice as much as in 2010. For a private company, that's better than fine.

But a public company has shareholders to answer to, looming institutional investors who will be clamoring for Facebook to find a way to rid itself of Zynga dependency, to find a way to turn your iPhone clicks into dividends. The company will have to answer for its rising costs and waning growth. Whether that answer comes at the cost of user experience, of your privacy and your security, remains to be seen.

Oh, and now seems to be as good a time as any to reiterate that however Facebook's IPO preforms, you won't be getting rich off of it. That's strictly insider/banker territory. It'll be fun to watch from the sidelines, though! [SEC]