I think a lot of those long term professional players do have gambling addictions, but as Norm Macdonald says: it's not an attiction when you're winning!
Gus Hansen surprises me. I know a lot of those tournament players are pretty weak in deep cash games and tend to play stakes above their level, but losing $20M... you'd think after $15M a smart guy like Gus would go: maybe I should put some of this money into an index fund or whatever.