I've long predicted that a virtual world-based currency would cross over and become a RW currency, and that there would be effectively no difference between game operator issued currencies and state issued currencies. That day is here. Over on Virtual Worlds News there's a report on MindArk starting a real, state chartered bank. Mind Ark's main game, Entropia Universe (fka Project Entropia) has long touted convertibility of the game's currency, the PED, into US$ (which are pegged at a constant exchange rate) as a principle benefit, and now they will have an in-game bank charterd by the Swedish Financial Supervisory Authority, and backed by government insurance. This effectivelly makes the PED a real-world currency.
There have been a few halting steps in this direction already (e.g. QQ Coins) This is especially interesting given Mind Ark's colorful history and team, and their involvement in the China Virtual Economy District (fka the Cyber Recreation District) project. It seems likely that this will move the PED beyond the world of Entropia very quickly.