Just found this interesting little article that's been doing the rounds in China about one of these online role-playing games that encourages people to spend lots and lots of money creating ever more powerful characters who then go and wage war, chop off heads and generally behave like complete beasts to everyone around them.
The game is so organised so that the more money you spend the easier it is to defeat your opponents. The game organisers encourage wars and thus spending. One player got disillusioned and started trying to act in a peaceful manner - fewer wars and killing, more alliances and trade.
It gets quite disturbing towards the end. Less about computer games and more about financial, sociological and psychological motivations behind it all.
I find these online games so weird - people buy and sell currencies used in the games: the World of Warcraft exchange rate is 1000 gold pieces to the dollar or something like that, and a few years ago another of the games had a GDP just above Bulgaria and just below Russia.
Anyway link:
The System
The article proper starts a bit down the page.