Sometime today, millions of people -- most of them in the U.S. and the Far East -- will check out of this world and into what economist Edward Castronova calls a "synthetic world." They are checking into online games including EverQuest, Ultima Online and Star Wars Galaxies.

Robert Siegel talks to Castronova, author of Synthetic Worlds: The Business and Culture of Online Games, and Robert Holt, an NPR video game reviewer, about the increasingly popular practice of using real-world money to aquire virtual gold pieces and more powerful characters.