This is the problem I see with the RMAH: I am firmly against money=power. I don't care if the only way to get power is through spending time in the game. That's the point. Actually getting your power by playing the game.
I realize that this may inconvenience people who have more money than time because they work a full-time job or whatnot, but here's my logic: if you don't actually dedicate yourself to the game and don't really play the game, why should you suddenly be as good as those who have spent time playing the game?
It isn't so important what someone spent (time, money) as the fact that they played the game.
In fact, going back to Extra Credits' episode on the Skinner Box, a well-designed game would give you most of your rewards by being generally fun to play to begin with. None of these "bring me 20 bear asses" quests, but "play through the content we've provided for you and you'll be justly rewarded".
Now, here are two possible extreme disasters that can happen with the auction houses:
A: Chinese kiddies playing in sweatshops undercut everyone even before cashing out so that they can depress the economy, and then $10 will buy you a fully-stacked toon on par with 60 hours of MFing/trading/questing/looting/grinding if not more. It'd really defeat playing so much of the game. Oh hey, you cleared the endgame content with some friends? Oh cool. Now instead of MFing/trading/etc. so you can solo the entire game, instead, you just buy the epic gear of the almighty for $10 and roll everyone who doesn't.
B: Chinese gold farmers buy up a crapton of gold to depress the exchange rate (EG $1 = 10000 gold) and suddenly, nobody can use the GAH anymore, leaving out everyone who can't/won't use the RMAH, literally turning the game into pay to win unless, once again, you can barter with other players like you can in D2. Because if you can't, then suddenly, trading just gets clean taken out of the game.
As for me, the fun part about D2 for me was grinding/begging/haggling/MFing my way to a stacked toon through in-game means. I mean I said "oh hey this is my first toon, I gave you some WPs, can I have some free stuff" and got a lightsaber that I traded for an arachs that I traded for Tal Rasha's armor and a spirit monarch.
Sure, I could spend $10 and get a fully stacked sorcy, but once again, that defeats the entire purpose of playing the game for me.