Perhaps not, but they do have the priority inbox feature that works nearly as well once it's been trained.

Who has time to train their own inbox?

Who has time to add their social graph to Facebook? If it's important to you, you'll find the time to do it.

My priority inbox was pretty much on the nose from the get-go. Only a few slipped by, and they were frequent mails from lists that I may have wanted prioritized anyway, as far as any computer system would know.

Seems like Google has a substantial "social graph" in the form of Gmail users and their contacts.