The power of links and the value of global knowledge

I think Paul overrates the value of the global view on such data. Simple link count works well for evaluation of the importance of the web page until the Heisenberg effect kicks in (people start to adapt their pages to score better in the algorithm). My hunch is that it is enough to know the local structure of a densely-connected social graph.

I think another HN reader as well as myself mentioned this earlier: Amazon has a <i>much</i> richer dataset than Facebook, and the context of purchasing when you visit the site. Their recommendation algorithms have cost me so much of my money, I don't even want to think about it. The implied and clustered behavioral data for advertising is all there, whether people are "friends" or not. The only thing I see that they lack is a buzzphrase like "social graph".