This has nothing to do with their address book. It builds off previous social meta-data efforts, especially FOAF and XFN. It's more an extension of their searc

This has nothing to do with their address book. It builds off previous social meta-data efforts, especially FOAF and XFN. It's more an extension of their search expertise, and it looks like they should be able to extend it with some of the latent semantic indexing stuff that they already do to make it a useful and powerful tool. What's innovative about it is the scale at which they are doing it.