The problem with the social network is that it's more personal than search. Search, while personal, can be made innocuous by keeping annonymous information. Th

The problem with the social network is that it's more personal than search. Search, while personal, can be made innocuous by keeping annonymous information. The holy grail of the social graph is to find out who the viral supernodes are. By that measure it's no surprise they went straight for the purchase history. If you can pinpoint the people who most influence other people you've got the potential for a very powerful statistic which can be fed into a viral marketing campaign.