Topic: Blizzard's Official Comment On Difference Between WoW's AH & D3's
Beverice, user on the Battle.net forums, pointed out in a previous blue statement Blizzard's stance on the purchase of virtual goods in their game economies, namely World of Warcraft.
The game's Terms of Use clearly states that all World of Warcraft content is the property of Blizzard Entertainment, and Blizzard does not allow 'in-game' items to be sold for real money. Not only do we believe that doing so would be illegal, but it also has the potential to damage the game economy and overall experience for the many thousands of others who play World of Warcraft for fun ... While we can understand the temptation to purchase items for real money, we feel that players can find ample equipment and money for their characters within the game through their own adventuring and questing.
Bashion reported back swiftly with this to say on behalf of Blizzard:
but it also has the potential to damage the game economy and overall experience for the many thousands of others who play World of Warcraft for fun
We still think that's true for a MMO in which thousands of players co-mingle in a persistent world and vie for supremacy in eSport competitions or 'world first' boss kills in raids. Neither of these are true though for a co-op action RPG.
The worst that could happen is you open your game up to the public, someone jumps in wearing some awesome gear, and you don't know if he found those items himself. But that'd be the case whether we offered an official way to buy items from other players or not.
we feel that players can find ample equipment and money for their characters within the game through their own adventuring and questing.
The same is not true for Diablo in which all items are randomized in both affixes and drop chances from all enemies. We know that trading is necessary in Diablo games to build a solid character as you could play forever and still never see a specific item you're after.