Stephanie Roberts is a 33-year-old parks service employee in a Chicago suburb where she lives with her brother and mother; in the winter, she drives the Zamboni at a public skating rink. But she's also Zania Turner, of glowing skin and impossibly luxuriant black hair, who sashays in silk dresses through the booming virtual world of Second Life, which is run by the San Francisco company Linden Lab. In her life as a 3-D cartoon, Roberts gathers with other avatars to role-play reënactments of obscure Star Trek cartoon episodes, build and buy digital homes and furniture, and hang out on digital beaches.

But Second Life is more than a game or a social-networking site; it's also a venue for financial transactions. The currency used within the virtual world, called Linden dollars, can be converted to U.S. dollars at a rate of roughly 270 to 1. More than $13 million worth of Lindens are in circulation, and 318,742 residents of Second Life--including Roberts--participate in its internal economy. "It's a fascinating and exciting place, because people are doing business in the absence of a lot of legal and regulatory structures," says Robert Bloomfield, a Cornell University accounting professor who studies virtual economies--and coined the term "metanomics" to describe the field.