Chances are, you are not going to take the news that players will be able to buy and sell items in Diablo III for real money very well. There are, however, a few arguments to be made in favor of the controversial system.
Last Tuesday, Blizzard unveiled the game's new auction house system in addition to numerous Battle.net related features. The auction house functions very much like the one in World of Warcraft, allowing players to place items up for sale and bid for existing listings, but with one key difference: players will be bartering in real currency instead of using in-game gold.
This certainly solves the dilemma of having to manage an out-of-control economy, but it creates a few new problems. Namely, the wealthiest players will be able to buy their way to the top. I would however argue that the implementation of real currency gives hardcore players huge incentives to keep playing the game, as luck and persistence would reward those who spent the most time in the game with actual pay-outs. It would also serve to eliminate the black market currently operated by gold farmers by putting every player on equal footing—at least in terms of who can make a profit.
Blizzard shares the same rationale. "If I have more money than time I can purchase items, or if I'm leet in the game I can get benefits out of it," said executive producer Rob Pardo.
Players familiar with the Diablo II auction site D2JSP will recognize the fact that players will attempt to make a profit off their gameplay, regardless of whether Blizzard creates an actual system to do so. The problems of using a third party website like D2JSP are immediately obvious—one has to trust the website, which is accountable to no one, not to divulge private information, and there is no way to take users who exploit the system to task. An official auction house sanctioned, and maintained by Blizzard itself eliminates these risks, and provides additional value to the player.
A not insignificant portion of the public may not approve of Blizzard's plan, but like it or not, auctions will happen regardless of Blizzard's involvement.
To curb abuse, Blizzard has set it so that it will cost a small fee to list an item on the auction house. Additionally, Blizzard will take another cut from processed sales. Both figures will be a flat rate, rather than take a percentage of the item's cost. Presumably, the stability of the auction house and its popularity will ensure Blizzard's continued involvement, and would thus be in the company's best interests to maintain it.
"Percentages really incentivize us to manipulate the system, and we don't even want the incentive to do that, much less actually doing it," said lead designer Jay Wilson. They don't expect to reap any profits from the sale of items, however. "We expect it'll break even," he said.
Ultimately, players can still choose to ignore the auction house which uses real currency, and play the game as they would without its existence. For these players, Blizzard has created a separate auction house that uses in-game currency in place of real currency.
Given that Diablo III is a closed, cooperative game with absolutely no massively multiplayer interaction—quite unlike World of Warcraft—there is no reason why any player should feel impacted by what other players do.