Gold farming is the practice of harvesting crap in online worlds with the aim of selling it for real-world money. Most developers frown on the practice, but that's not stopping an estimated 100,000 people from doing it.
A report from the World Bank reckons that, across China and Vietnam, "up to 100,000 people" are toiling away in online gold farms. Interestingly, these human farmers only account for around 30% of the global market in virtual goods, with the remainder split between "bots" that play games automatically and revenue gained from the theft of legitimate accounts.
As the report states, that kind of money of that kind of scale means that, while gold farming is a pain in the ass for the developers of online games, it can actually have a beneficial effect on the development in certain regions by bringing in cash.