Ask HN: Has the GMail graph been published?

When GMail launched, it was invitation-only, and there was a limited amount of invites to give away. My immediate thought was that Google was building a graph of all users, and that the nodes were being kept artificially small in purpose for some reason.

The other immediate thought was the prevention of spam agents using GMail for their purposes.

Sampling users a few at a time, starting with trusted users, also enabled the creation of a profile of a "good user", to further prevent spammers from using GMail--their profile would be very different.

Is there any publicly available graph of GMail or other email systems, quantifying the connectivity of the users (I expect a power law)? And any analysis of GMail "good" and "bad" users?