With a small stake in Zuckerberg's social network dynamo, it is only natural for Microsoft to lean on Facebook to challenge Google's dominance in the search engine arena. Simply put, Microsoft's Bing is now more tightly integrated with Facebook's horde of user data. Search entries on Bing or Facebook would reveal more than just search results hence, including friends' Facebook profiles or the relevant "Like" pages.
Telegraph.co.uk - Microsoft’s search engine Bing will now be incorporated into social network Facebook, allowing American users to see integrated results. The development means that search results will be combined with information about whether Facebook users’ own networks like specific sites. When a user searches for a film, for instance, information about how many of their friends “liked” it on Facebook and related links they have shared will now appear alongside the results. Restaurant recommendations and links will also be featured.
Note that this integration is only applicable to the States at the moment. Read more about it here.