Bernie Maddoff is in jail for the next 150 years. He misled investors with a Ponzi scheme, a scam in which you promise people a high return on investment, which you pay not with any real business, but with the money new investors give you. In real life, this is fraud, and if you are caught you will go to jail for it. In a game, for example if I offer you a dodgy deal for a street in Monopoly counting on the fact that you are bad with numbers, this is part of the game and I won't go to jail for it. It's just play money. But what of situations that are in between?
The big EVE news this week was about the biggest scam ever, a Ponzi scheme netting the fraudsters 1 trillion ISK. Now we can cite the monopoly example and consider that just play money. But ISK aren't just play money, they can be converted into real money. Depending on the exchange rate the 1 trillion ISK is worth between $38,000 and $52,000 of real money. A previous case of fraud in EVE was reported as somebody stealing ISK, who exchanged it for real money, and "used the cash to put down a deposit on a house and to pay medical bills". If you can pay your real world bills with it, it isn't play money any more.
From EVE to the EQII Station Exchange to the Diablo III real money auction house, the link between virtual items and real world dollar value is getting stronger all the time. And at some point the legal protection has to kick in. Running a ponzi scheme in a foreign currency won't protect you from the law, so why should it protect you if that currency is a virtual one? If money stopped to be in the jurisdiction of the real world as soon as you transformed it into virtual currency, we would have created a legal way to launder money. I do not think real world governments are going to agree.