thread on the forums; so far, the biggest anyone's found is 341,462, on a druid named Kuroma from US-Daggerspine-A. Can anyone beat that? Armory links or it didn't happen.
Update: We have a new champion already! Theplague, of EU-Frostmane H, with 411,701. Anyone want to step up to that?
Update 2: Fartzwrgoben (does that name mean anything?) of EU-Perenolda-A, a subtlety Rogue, handily tops that with an astonishing 560,878!