Have a look at Ray King's essay:
http://www.pint2.org/index.php/Contributor_Ranking_System
Although this solution is aimed more generally at sites using Wikimedia software, this is something I believe Ray has been talking with Jimbo about. I happened to be present when Ray presented this the other night, & a known expert suggested an excellent way to grab some of the data needed without causing a strain on the servers.
And Ray is *very* interested in feedback. I hope he concentrates on a simplified version of this proposal, rather than trying to write the finished, with all of the bells-&-whistles version.
Geoff