So the new web is semantic & social and search is important. Facebook has made its play for the first two, and the assumption is that it's going to make a play for the third (search) as part of its new web land grab (AKA Kill Google).
But even if Facebook is serving up billions of Like buttons, whilst that means it can theoretically catalogue the web and apply personalised recommendations, it still has to do the engineering. And whilst Facebook isn't short of clever developers (quite the opposite), its 300 engineers have nothing like the firepower required to beat Google at this (I know this is hardware not software, but as an indication of the size of Google it’s pretty impressive - http://bit.ly/cbktww).
With valuations where they are there's nothing to prevent Facebook from acquiring the rocket scientists it requires - but why bother? 99.9% of the web is still unstructured, and making sense of that is Google's home ground (great Wired article on search query semantics here - http://bit.ly/9i6kYg).
What is really required (by us, the users) is a combination of the two – Google’s algorithmic scientists and search experts working with Facebook's recommendations and social graph. This would give us what we want – a searchable, personal, semantic web. And this begins with Google adding the Like button to its search results. (And ends, slightly unrealistically, with Facebook allowing Google to index its data).
Of course Google doesn't own part of Facebook, Microsoft does. So the best we can hope for in the future is something like this, but using Bing - FaceBing, or perhaps BingBook?
In the end this is all about ad revenue, and no one seems inclined to share that right now, so although it makes for an interesting user experience / engineering challenge, it's not going to happen.
[Update: Not sure when this appeared, but the Facebook developers’ site search results page now sports a natty blue Bing logo. Has Microsoft out-flanked Google with its purchase?]