Facebook is quietly doing an amazing work with Autosuggest. Until a couple of days ago, Autosuggest was a method to find People. Now it’s a true personalized search tool where Facebook is injecting articles posted by your friends (see below on the left), Wikipedia pages (see 2nd result below on the right), question and answers (see 3rd result), Facebook pages (4th result). I believe that the experience with Facebook is potentially more exciting that the one exposed in Google Instant. Apparently, they are trying to move away from the SERP paradigm.
Update: they also have Web pages where users expressed a "Like it". So they are effectively crawling them (or at least leveraging the "Like" anchor). Is Facebook starting to become a true search engine?