Researchers are apparently using economies in virtual worlds like Everquest, EVE Online, and of course our own World of Warcraft to determine how real-world economies work, according to this article by Reuters. Scientists have, of course, used WoW to model real-world behavior before, but that was specifically for something biological, and thus there were quite a few differences between the virtual model and the real application. In economies, however, it's all just money and numbers, so researchers can easily see real patterns and movements in the data.
Unfortunately, the article doesn't go too deeply into their results (and it only talks about their findings from Everquest), but there is one nugget of conclusion: the economists saw inflation spike in one server over 50% in just five months. They say that the population rose on the server, which apparently made some items hard to find, thus raising prices. Economists say they've seen that same thing in the real world before: in developing nations, and in war zones. We can probably see similar effects right around a patch, or even just on weekends. As more people run to the AH to buy certain items, inscriptions or enchants, the price on those is going to rise. Interesting stuff -- it would be cool to hear what other similarities these guys have found between the virtual world and the real.