The Early Edition on CBC Radio One had an interesting piece this morning about criminals using on-line video games, or virtual property used in on-line games, to launder money. The scenario is that a rogue will use stolen credit card information to buy virtual property (items, currency, etc.) on one of the various virtual property exchanges, shuffle that property between various in-game characters to obfuscate the trail, and then sell the property on the same or a different exchange in return for cash.
The extent of this activity isn't clear, but apparently it's common enough for law enforcement to be taking notice.
An interesting related question is what if you (a legitimate game player) use in-game currency to buy in-game property from such a rogue — are you a bona fide purchaser, or are your new favourite Doomhide Gauntlets subject to confiscation by the authorities as proceeds of crime? Let's see if it ever comes up.