>google should most definitely be scared. they make something like 90% of their profit from advertising - advertising based on your search query or the context of the page you're reading. facebook's ad platform has the potential to destory them, given they know your so much more about you, your friends, interests etc.

I suspect that your query stream is much richer data than everything you've ever done on facebook.

>is it hard for facebook to launch a search engine, with rankings tweaked via the social graph? not really.

This is dramatically underestimating the difficulty of search. Ranking sites by quality is not hard (in the head at least), and facebook can certainly tweak that well with social data. Ranking pages by relevance to a query is extremely hard.