If you are one of the millions of Facebook users who play games like Playfish or Pet Society, you are a datum in Kristian Segerstale’s behavioral economics experiments.

Instead of dealing only with historical data, in virtual worlds “you have the power to experiment in real time,” Segerstrale says. What happens to demand if you add a 5 percent tax to a product? What if you apply a 5 percent tax to one half of a group and a 7 percent tax to the other half? “You can conduct any experiment you want,” he says. “You might discover that women over 35 have a higher tolerance to a tax than males aged 15 to 20—stuff that’s just not possible to discover in the real world.”

Note that these are virtual goods that are sold through the game for (literal) money.  And here is the website of the Virtual Economy Research Network which promotes academic research on virtual economies.