"We tried to acquire Facebook," Fritz Lanman, Microsoft's Senior Director of Corporate Strategy and Acquisitions, told an audience Dec. 9 at the Le Web '10 conference (as reported by TechCrunch). "Facebook had a lot of similarities to Microsoft back in the day."

According to David Kirkpatrick's "The Facebook Effect," Microsoft CEO Steve Ballmer visited Zuckerberg in Palo Alto, Calif., where he made the $15 billion offer. But Zuckerberg wanted to keep control of his project. And what's that compared to enough money to buy a medium-sized country?

Microsoft did invest in Facebook, however, to the tune of $240 million. That was good for a 1.6 percent stake in the social network, which has collaborated with Redmond on a number of initiatives over the past few months.

In October, Microsoft and Facebook announced a deeper partnership centered on a set of new social-search features accessible via Bing and Facebook's Web results. One feature, Liked Results, displays Websites and links "liked" by a Facebook user's friends. That's paired with Facebook Profile Search, which leverages a user's Facebook connections to deliver more relevant results.

"We think it's time for a real, robust, persistent social signal," Satya Nadella, senior vice president of Microsoft's Online Services Division, wrote in an Oct. 13 posting on the Bing Community blog. "Facebook has led a transformation of the Internet already. It has reached and passed 500 million members, and the amount of content created inside Facebook each day is staggering."

The following day, Microsoft announced updates to its Docs.com online applications platform, which allows Facebook users to create and share Word, Excel and PowerPoint documents. The new features included .PDF support, full-text search, user-generated templates, and drag-and-drop Silverlight document uploading.

Such collaborations with Facebook, of course, give Microsoft access to a massive brand and a built-in audience, both of which are vital as it seeks to battle Google Docs and similar cloud-based productivity platforms. For Facebook, collaboration with Microsoft on a project like Docs.com allows the social network to expand its utility to users in new ways.