Facebook does many things well but search still isn’t one of them. Over the past year Facebook has taken steps to improve its search usability; and Microsoft has been working with Facebook to do a better job with web search on Facebook.
Search remains a major opportunity for both Facebook and Bing, which hasn’t yet been fully realized. It’s not clear how “motivated” Facebook is to succeed as a search engine at this point however.
According to the All Facebook blog Facebook has slightly redesigned its SERP to make it more consistent with other pages. In particular the left nav/filters have been updated to match the rest of the site.
Although comScore seems to have stopped reporting its “expanded search” metrics, in May of this year Facebook was one of the top 20 “search engines”: