This is a really good idea. If they can get the right games on board. Also if they can figure out a way to deal with taxes. Diablo 3's real money auction house was basically shutdown because the US government wanted their piece of the pie and it sounds like Blizzard didn't have a real way to do that.
With game publishers wanting to get more money out every game it was a matter of time before the government wants a piece of something they had nothing to do with. But I agree, a bunch of publishers and game development studios are just not finding ways to do it correctly, for now.