Systems do react, and that reaction is why you can never predict system behavior with extrapolation.
Neil Stephenson posits a more rational economic system for WoW (and presumably Diablo 3) in the novel Reamde. What is perhaps most interesting is how he deconstructs the flow of 'value' in the economy, trickling in from gold creation and trickling out with taxes and purchases. To bad Blizzard didn't read that first.
That said the notion of a 'no levels' RPG where everything is trained/earned is more like Everquest (nobody wants to go back to skinning 6,000 rabbits, trust me) but it is the place where the next big breakthrough will be made. And it will make the people who discover the recipe very wealthy indeed.