If you can count a piece in Wired magazine as proof, that is. They have an article
online adding to the current discussion about the business building skills inherent in MMOG's.
The article focuses on Stephen Gillett, a director of engineering operations at Yahoo, who also happens to be one of the top guild-masters in World of Warcraft. And yes, he attributes some of his success to the lessons learned while playing multiplayer online games.
I've got the gameplaying part down...now if Yahoo would just come knockin' on my door...