Massively multiplayer online economies
The Baltimore Sun is carrying an article on people who spend quit a chunk of their time immersed in virtual worlds, whose posessions and money can be traded in the real world for cold hard cash:
Companies in China pay thousands of people, known as “farmers,” to play MMORPGs [massively multiplayer online role-playing games] all day, then profit from selling the in-game goods they generate to other players for real money.
Trade in virtual items is now worth more than $100 million each year. In some Asian countries, where MMORPGs are particularly popular, in-game thefts and cheats have led to real-world arrests and legal action.
In one case in South Korea, the police intervened when a hoard of in-game money was stolen and sold, netting the thieves $1.3 million.