Interesting and long post by Danny Sullivan, in reponse to the recent Scoble linkbait that Google will be killed by Facebook, their social graph, Mahalo, etc. The post covers a ton of thoughts, most of which I agree with.
There's a better way than Mahalo. A "people-powered search engine" like Mahalo will have a tough go, because it will be tough to keep up with the maintenance and link rot.
Kevin Burton thinks that it's about the social graph augmenting the web graph, and Google can index both. Yes, that's true, but I think there's more to it still.
Today's social search revolves around too much damn effort -- friending, voting, bookmarking, etc. As Danny points out "people don't want to build search results -- they just want to search". This is why I believe social search can't be derived from explicit votes/gestures, and I don't think it will be limited to people within your social network.
There's a new graph coming, called the "implicit graph". No effort involved to contribute, and social groups (formed implicitly) filter the web graph for us.