If you're a fan of nice round milestones, you'll like this: Facebook welcomed its 200 millionth active user yesterday. Founder Mark Zuckerberg blogged about the huge number, illustrating how far the social-networking site has grown in five years.

Not everyone is celebrating and throwing confetti, though. Yahoo! (NASDAQ:YHOO) is probably feeling like it broke up with the girl who grew up to become a supermodel. Its supposed quest to acquire Facebook a few years ago proved fruitless.

Microsoft (NASDAQ:MSFT) got closer to sealing the deal, but wound up paying $240 million for only a 1.6% stake. Facebook naturally wasn't worth $15 billion at the time. Microsoft's investment was really just a cover charge. However, it too blew it by not swallowing Facebook whole.  

You won't find any Google (NASDAQ:GOOG) fingerprints at the scene, and that's surprising since Google has been an early bird with some of its acquisitions, such as Blogger and YouTube.

What is it with the three leading search engines and their inability to nab the social-networking sites that ultimately matter? As the Internet's traffic cops, you would think that they would be the first ones to sniff out hot website trends. Instead, history finds News Corp. (NYSE:NWS) buying MySpace and Time Warner (NYSE:TWX) bobbing for Bebo, while fast-growing Facebook remains a free agent.

Three of us Fools couldn't agree on what Facebook was worth -- it was either not much, $3 billion, or $15 billion -- back when Facebook supposedly had just a third of the audience that it watches over today.

As the voice behind the $3 billion valuation, I don't feel like tripling my price, but how stupid was Yahoo! to let Facebook get away when it could have had it for $1 billion or so? That price today would translate into just $5 for every Facebook member.

Facebook has not been an easy site to monetize, but its viral ways should leave you drooling over the possibilities of what Facebook can do in the future.

So congratulations, Facebook. My condolences to the failed suitors.

Some cool widgets for your Facebook profile:

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Microsoft is a Motley Fool Inside Value selection. Google is a Motley Fool Rule Breakers recommendation. Try any of our Foolish newsletters today, free for 30 days.

Longtime Fool contributor Rick Munarriz remembers when social networks were an offline endeavor. He does not own shares in any of the companies in this story. He is also a member of the Rule Breakers analytical team, seeking out the next great growth stock early in its defiance. The Fool has a disclosure policy.