Blizzard is trying a new system with Diablo 3, they will be allowing players to sell their items for real money with the in game auction house - with Blizzard of course taking a percentage of the cut. If it works well, expect them to implement it in their next MMO as well.
They are now the virtual e-bay. Collect fees on what players sell. This is their way of combating the gold farmers and bots. Gold farming and botting will happen no matter what, they realize that, and instead of fighting them, why not charge em a few to actually sell.
If this is a success, expect the same to migrate over to WOW. Gold selling is a billion dollar business. If they can tap into that, it will definately add to the bottom line.