As we all know by now (and the rest of the world is rapidly learning), the imaginary currencies that are earned, spent and traded in massively multiplayer online games and other virtual worlds are anything but virtual, themselves. While no government authority stands behind them to insure their value, a seal of approval isn't needed for a currency to become "real." A World of Warcraft gold piece is worth as much as you can get for it on the market - about $0.10 at the moment. The U.S. dollar derives its value in exactly the same way.