* FB hasn't really given search a big go yet. They're working on getting onto everyone's phone. I think that's too early to call.
* Apple bought Lala & has PING. Neither were great successes.
Facebook is building a search engine. They are very proud of their "natural language" graph search. If they expand that to web sites they will likely fail.
Apple is starting to look at social with things like Facetime. But they are looking at it as a feature not a core business.
I'd be interested to see them try, because I have no idea what they could offer that I don't already get from the plethora of search engines available. I think Bing already has some social search thing that pushes up searches done by friends or something, but I don't hear much about that at all.
They also have an increasingly insightful record of your personality. Probably moreso than Google, since Facebook gets more of your "casual" life than Google.
Google is in a good position to record and analyze the intents you express, but Facebook likely has a better record of who you are outside of those expressed intents.
Turning that into a useful product is difficult, but I'd be very surprised if they never work in that direction.