Wired is running a story about a research paper out of the University of Wisconsin-Madison which discusses how some games get players to do scientific research without them explicitly realizing it. The paper itself is also available. Quoting:
"... we examine the scientific habits of mind and dispositions that characterize online discussion forums of the massively multiplayer online game World of Warcraft. Eighty-six percent of the forum discussions were posts engaged in 'social knowledge construction' rather than social banter. Over half of the posts evidenced systems based on reason, one in ten evidenced model-based reasoning, and 65% displayed an evaluative epistemology in which knowledge is treated as an open-ended process of evaluation and argument."

http://science.slashdot.org/article..../09/10/0142251