(Source) While technically not a MMO, one of the most anticipated PC games in recent years added an element of MMO to its core features. Introducing the auction house system in Blizzard’s Diablo III, where not only can items be traded using in-game gold, but real cash as well.
I am not sure if this is a good thing, since people can earn some money for their trophies while the rich players will, similar to most Asian online games, dominate the game. Not forgetting there will be PvP in Diablo II as well. I hope this is not a wrong step for Blizzard.