Q u o t e: Players will use whatever they want as currency, if gold fails we use items, what is the problem?
in my post, i address this question. If they build an AH system based on gold as currency, it will be for naught because the players chose to use a different system.
I simply dont believe blizzard would make any sort of complex trading system that allows players to dictate what they want to trade without the use of a predetermined currency.
Also, it would be much more convenient for the next currency to not have to be stockpiled in your inventory, but rather have its on section in the UI that shows how much you have.