I think only ~50% of google's revenue comes from adwords. That's leave's 50% as a target for facebook. Also there can be other ways to measure intent. For exam

I think only ~50% of google's revenue comes from adwords. That's leave's 50% as a target for facebook. Also there can be other ways to measure intent. For example analysing content of chats or status updates in real-time. And given large amount of IPO cash + huge user base, maybe facebook can build a good enough or interesting search engine that could draw users. Also , facebook's data could be the basis of TV ad targeting when internet TV becomes the norm. So there's another revenue source. On the other hand, google can combine all sorts off data to get strong targeting, so it's not clear who will have better targeting.