Facebook partners with Bing to add social juice to your search results
Facebook will also factor into Bing's improved people search, popping up people you're more likely to know, so you have a better chance of finding the right "John Smith." This feature will roll out gradually to Bing users in the coming weeks, so don't be too surprised if you don't have it.
Bing is the latest in Facebook's select group of "Instant Personalization" partners, along with another Microsoft project, Docs.com. Instant Personalization gives these sites special access to your Facebook data and friends, so they can provide features like the ones Bing just announced. If you don't want to share it, you can opt out of Instant Personalization entirely from the Facebook Privacy Settings screen.