In detailing the list of improvements and changes that Diablo 3 brings to Battle.net (persistent friends list, cross-game chat, PVP matchmaking, etc.), the ability to auction off items for real-world money stands out the most. Essentially, Blizzard has taken the seedy world of third-party gold and items or characters for money trading, and institutionalized the practice.
Executive vice president of game design Rob Pardo describes the currency-based auction house as a solution to a multitude of economy-related problems from previous Diablo installments. People used to have to drop items on the floor and click with blind faith that they were getting what they expected. Websites that were basically nothing but fronts for scammers would prop up to capitalize on the exploitable (through duplication and manipulation of client-side characters) economy. Even trying to make the transaction was annoying, as you’d have to put up with players constantly spamming the chat channels with item listings.