The rumor had been that Microsoft would give Facebook the valuation it wanted to keep the relationship out of the hands of Google. "This deal marks an enormous advertising syndication win for Microsoft," said Kevin Johnson, president of the Platforms & Services Division at Microsoft.

On the conference call Johnson justified the valuation and the investment, saying that Facebook "has the ability to get to 200 to 300 million users." Johnson also suggested there was more to the deal than the public announcement indicated.

Facebook's Owen Van Natta declined to mention whether there were any other investors in the round. He also said that the Microsoft investment wouldn't affect the Facebook platform and third-party developers. Van Natta suggested in response to a question that the partnership may include paid search, but he declined to confirm that. For now it appears to be about display ads and "ad types that are unique to the social experience," explained Johnson.

In response to questions about monetization, Johnson declined to offer specifics: "We continue to see improvement in the monetization of the Facebook ad inventory," he said. Van Natta said that the Microsoft money would be used to grow and improve the infrastructure as well as for hiring, which he said would continue to ramp up next year.

While it's not a certainty, this makes an eventual Microsoft acquisition much more of a possibility.