I would read the announcement section about auction houses as this has been discussed to death. ; )

The way to do it is introduce a dynamic exchange rate for gold to crystals. You set a maximum gold amount in the system, say 1 billion and a minimum amount of crystals in the system ( you amend/review as player numbers grow). You then allow players to hoard gold and convert to crystals and vice versa.

Add supply demand dynamics to the card pool and you have a fully functional market place without damaging those who have hoarded gold but also giving new players equal chance to trade. You could even go as far as introducing a 3rd currency but don't want to over complicate the AH!

Before I get trolled, I'm a commodity trader that's how markets work. It's more about he coding of the exchange rather than the actual system... Either way I can't wait.

Like the idea about buying pre designed decks etc ; )