Facebook is still learning how to make money off of all it knows about you. And it will probably be learning for years, just as Google has evolved over time. But here's a simple example that drives home the potential, says Landis.

Say you're a wedding photographer. When you give Facebook your ZIP code and some money, it can show your ad to all the people near you who have indicated on Facebook that they just got engaged. Powerful stuff, which Landis says can help businesses overcome their age-old gripe about marketing dollars -- that half of their ad budget is wasted but they don't know which half.

Three key surprises in the filings confirm all of this:

● Facebook has operating margins of 50%, compared with Google's 24% when it came public, says Vandeventer. This profitability gauge measures earnings before costs like interest and taxes. "We're looking at a very profitable business," he says.

● Facebook earns net margins -- the bottom-line profit margin -- of 27%. That's the $1 billion in earnings from $3.7 billion in revenue. "You just don't see that very often," says Tom Taulli, an IPO expert who writes for InvestorPlace. "It's definitely a monopoly platform like Google. And these types of monopolies have off-the-charts profits and high barriers to entry."

● Average revenue per ad jumped 24% in the fourth quarter, compared with the year before. "That is really good pricing power, really out of the ballpark," says Vandeventer. Pricing power is a key sign of strength in a company, and a quality that ace investor Warren Buffett always looks for.

Those are numbers the other recent social-media IPOs simply can't come close to.

Takeaway No. 3: Shares should debut at $35 to $40

Vandeventer estimates that there are 2.6 billion Facebook shares outstanding. Given the leaked estimates that its IPO will net a market cap of $100 billion or somewhat less, this suggests that Facebook will debut with shares in the $35 to $40 range.

This estimate makes sense for a number of other reasons, too. First, Facebook shares currently trade for about $30 to $33 in the private markets where the stocks has been available for some time. And if you put the same multiples on Facebook that Google carried not long after its IPO, you get to the same ballpark of $35 to $40.

Of course, Facebook likely won't have its IPO until May or later, and the company will release first-quarter results before then. If those results show really impressive growth, that $35-to-$40 range could rise, says Vandeventer.

That price, of course, is available only to privileged investors with large enough brokerage accounts at the right brokerages, like Goldman Sachs Group (GS, news) or Morgan Stanley (MS, news), to get early access to shares. In the first day of trading, Facebook stock could zoom higher, as social media IPOs like LinkedIn (LNKD, news) did last year.

This why most investors need to be careful not to overpay on that first day or on any early spike. Hot IPOs can have wild volatility in the early days because of all the enthusiasm.

If the price soars, wait. Facebook will likely have a lockup release 90 days or 180 days from the IPO, which will allow insiders to sell huge amounts of stock. This could create a dip, and a better chance for most investors to get in.

Takeaway No. 4: Facebook faces real risks

The opportunity to invest in even the clear leader in an evolving space like social media comes with a lot of risk.

Theoretically, Facebook could end up as the next MySpace or Friendster, its social-network predecessors. In reality, the company is so good at what it does that it's unlikely it will get pushed aside so easily. Its vast membership proves this.

Instead, one risk that really bothers me is simply that a big part of Facebook's business is display advertising. By most accounts, that's not a great business.

A key advantage is that Facebook knows so much about its users. But any kind of specialized site can make a similar claim. A website dedicated to weddings, for example, knows its users are interested in themes like starting a new household, children and, of course, wedding planning.

A good comeback is that Facebook has a wider range of much more targeted personal information to sell against. "Facebook ads have a decent return on investment to smaller clients," says Kenneth Wisnefski, the CEO of WebiMax, a social media marketing firm in New Jersey. "We worked with a company that sold vintage Bruce Springsteen memorabilia. They did great on Facebook, because they were able to reach the group they wanted to reach."

But Wisnefski wonders if Facebook will be able to perform the same magic for larger companies that sell products that aren't nearly as niche -- but which have much bigger ad budgets.

He's not alone. "I have contacts who advise on how to spend advertising dollars at Facebook, and they are still trying to figure out what the return is," agrees David Rudow, a tech sector analyst for Thrivent Asset Management. "Just because your friend bought a Whirlpool washer doesn't mean you're going to buy one, too."

One solution may be to make money off a payments system, the way eBay (EBAY, news) does with PayPal. This is in the air with Facebook, given that PayPal co-founder Peter Thiel is a big Facebook investor. But here, Facebook might suffer from the Best Buy (BBY, news)effect, which has people using the retailer as a showroom before going off to make purchases elsewhere, presumably online. "Facebook wants you do everything on the Facebook platform, search and buy, but what is to stop people from going outside the platform?" asks Rudow.

Another fix for Facebook would be to get more aggressive in using what it knows about you to serve up ads more forcefully. "But the risk is that they know too much. So if they push too hard on marketing, will people get creeped out?" asks Rudow. "They need to be able to do it in a way that doesn't upset the masses," agrees Wisnefski.