After years of waiting for a peek behind Facebook's financial curtain, the company finally filed its prospectus for an initial public offering on Wednesday, seeking $5 billion in funding. It's on track to become one of the largest IPOs in tech company history.

An exciting time for investors and Wall Street, no doubt, and the S-1 filing will most likely be scrutinized for some time to come. But unless you're working for Goldman Sachs, you're probably not well-versed in the ins-and-outs of stuffy financial paperwork.

We've taken a quick and dirty look at some of the juicier bits of Facebook's filings. Here's what jumped out at us the most.

Photo: Courtesy of Zynga

Zynga's Massive Footprint

We knew Zynga was going to be featured prominently in the S-1 – the foundation of Zynga's core business is built atop the Facebook platform – but we didn't know just how much Facebook relied on Zynga.

The social gaming company accounted for 12 percent of Facebook's annual revenues in 2011, a massive figure derived from payment-processing fees involved in the sale of Zynga's virtual goods as well as advertising purchased by Zynga directly. Furthermore, each of Zynga's social games produce a significant number of additional pages against which Facebook can sell display advertising, boosting revenues all the more.

In other words, while Zynga still needs Facebook, Facebook is quite attached to Zynga – so much so that Facebook includes the data in its "risk factors" section.

Photo: Jon Snyder/Wired.com

Mobile Is Huge, but Still Not a Moneymaker

Facebook has made it clear for some time: Mobile is the future. Led by CTO Bret Taylor, the company will continue to focus on HTML5 development for mobile devices.

It's a good thing, considering 425 million people visited the site on a mobile device in the month of December. That's over half of the company's user base.

What's worrisome, however, is that Facebook's precious ads aren't being served up to mobile users. Read that again: Facebook's main revenue stream is lost on over half of the 845 million users coming to the site in December. If that trend continues and Facebook fails to monetize mobile quickly, it's not a pretty sign.

A Twitter-esque Move: Sponsored Posts

Speaking of mobile, Facebook could be working on a way to monetize site visits from phones and tablets. And the company may take its cues from Twitter.

The S-1 states that the increasing growth of mobile remains a risk for the company until it can successfully monetize the platform, which could include inserting "sponsored posts" into users' news feeds on mobile devices. While Facebook doesn't go into what that is exactly, it seems akin to Twitter's business strategy with the incorporation of "promoted tweets" – Twitter messages paid for by companies and featured prominently at the top of Twitter users' feeds.

Facebook allows that it could attempt to deliver traditional display ads on of mobile devices, though we're having a difficult time thinking that through, considering the form factors. Tablets? Maybe. Phones, difficult.

Photo: Wired

User Activity Remains Boisterous

Yes, Facebook's user base is massive. At 845 million unique visits per month, nearly one sixth of the world is visiting the site.

But they're doing more than that. Daily user engagement is up in a big way, scaling from 200 million daily active users (or DAU, in Facebook's S-1 parlance) in March of 2009 to over four times that amount as of December of this year.

And most of that growth is coming from outside of the United States. The key areas, Facebook states, are Brazil and India, with 37 million and 46 million monthly active users (or MAUs) in December.

No Stranger to IP Lawsuits

The knock-down, drag-out court battles of Valley giants Google, Oracle, Microsoft, and Apple (among many others) have been splayed across headlines for months. Everyone wants a piece of everyone else's profit pies, and intellectual property lawsuits based on patent claims seem the best way to go about it. Suing your competitors – and, in some cases, even your manufacturing partners (I'm looking at you both, Samsung and Apple) – is commonplace.

Facebook isn't exempt. "Defending patent and other intellectual property claims is costly," Facebook acknowledges. In the course of this it "may receive unfavorable preliminary or interim rulings" in its cases. As a result, "there can be no assurances that favorable final outcomes will be obtained in all cases."

It's Still Zuck's Site

The amount of shares owned by executives and other investors has been speculated upon for years, though we've known that Zuck has always been the largest shareholder.

What's surprising, however, is how wide that margin is between Zuck's stake and the next in line. Zuckerberg owns more than half a billion shares of the company, amounting to a 28.4 percent stake in Facebook. The next largest individual shareholder is James Breyer of venture capital firm Accel Partners, with fewer than half that amount of shares.

Interestingly enough, outside of Zuckerberg and Breyer, there's only one other individual who owns a relatively significant percentage of the company who is neither an employee nor an investor: Co-founder Dustin Moskovitz. He owns over 130 million shares, or 7.6 percent of the company.