In a weird way this week's news about Chinese prisoner being forced to farm gold in MMORPGs ties in with my previous post about buying virtual items in MMORPGs: If game companies don't sell virtual property, and the only way to get that virtual property is by hard, grinding labor, then a black market which basically sells that hard labor is going to evolve. Whether that is a prison camp or a sweatshop, in China or in some other part of the world, they all sell virtual labor for real money, because virtual labor is the only thing that counts in MMORPGs without an item shop.
A game which has the option to buy virtual goods directly from the game company destroys the business model of the sweatshop gold farmer. Unlike real labor producing real goods, virtual labor to farm virtual goods is based on the artificial scarcity of those virtual goods. As this scarcity isn't real, the game company has total control over the supply, and can always produce virtual items for cheaper than a gold farmer can farm them for. By having legal ways to buy virtual goods, the illegal and morally wrong ways to these goods are made obsolete.