I would assume it better to compare and make predictions about me based on somebody unknown to me but with strikingly similar purchasing habits, than to compare

I would assume it better to compare and make predictions about me based on somebody unknown to me but with strikingly similar purchasing habits, than to compare me just to known associates. Part of the problem with the social graph, particularly as it exists on broad networking sites like Facebook et al, is the lack of data about the nature of those relationships. (ie, "the more you know about them"). I've got however many dozen friends, but the social graph there doesn't distinguish between the guys I went to primary school with and the guys I see every weekend. If I could better position my relationships, more accurate data could be created. Eg, if I declare Dave is my 'drinking buddy' and Dan is my 'film friend', the system could make reasonable predictions about what I might like to drink based on Dave and what films I might watch based on Dan, while ignoring the vice-versa. In other words, the value of the social graph requires more meaningful information about relationships, not just more people. Without that, aggregated data wins out. You're right - pure speculation is cool!