William Sims Bainbridge Virtual worlds are persistent online computer-generated environments where people can interact, whether for work or play, in a manner comparable to the real world. The most prominent current example is World of Warcraft (Corneliussen and Rettberg 2008), a massively multiplayer online game with 11 million s- scribers. Some other virtual worlds, notably Second Life (Rymaszewski et al. 2007), are not games at all, but Internet-based collaboration contexts in which people can create virtual objects, simulated architecture, and working groups. Although interest in virtual worlds has been growing for at least a dozen years, only today it is possible to bring together an international team of highly acc- plished authors to examine them with both care and excitement, employing a range of theories and methodologies to discover the principles that are making virtual worlds increasingly popular and may in future establish them as a major sector of human-centered computing.
