This isn't a rumour. This isn't even a speculation. This is just the New York Times saying that Bing is killing Microsoft from the inside, and that if Microsoft wanted to sell, they could maybe do worse than Facebook. Agreed!
Here's the thing: It's no secret that Microsoft loses gobs of money on Bing, quarter after quarter, and year after year. It's also no secret that Bing will remain a viable property, if for no other reason than it's Google's only serious competition. Also, it's fun to say.
Facebook, meanwhile, could use a robust search offering to counter Google, especially now that Google+ has set itself up on a nice little tract of Zuckerberg's sandbox. Bing already incorporates Facebook in its results; full integration would make for the first truly social search experience, and the only real point of differentiation for a Mountain View alternative. And it's not like Facebook's lacking for cash.
So again: not a rumour. Not something that could or might happen, not right now. But something that should. For Microsoft, for Facebook. And for you. [NY Times]