PageRank was based on a big graph: the links that make up the web. The next breakthrough, many argue, will be based on the social graph, the links between us all. Facebook is clearly based on this insight. If you are interested in this issue, and feel it’s important (I do, in particular, who owns and profits from this information), read this write up from Brad Fitzpatrick who, it turns out, started at Google….today. Also working on this is David Recordon, who is going to Six Apart to work on these ideas. Interesting!