Recognized by the Guinness Book of World Records as the most popular MMORPG (massively multiplayer online role-playing game) in videogame history, World of Warcraft is everywhere -- from episodes of South Park and The Simpsons, to online series like Watch the Guild, accolades and awards from game critics, and prime-time commercials with Mr. T. Inevitably, such a cultural phenomenon triggers deeper questions. When does an assumed identity become real? Does the Corrupted Blood epidemic warn us of future public health catastrophes? What are the dangers when...