   University of Texas professor's article on addictive games
  http://www.utexas.edu/features/If it''s not there, go to the archives since they will probably update that page with the latest feature soon.  I thought it was a good read.  I''m sure good game designers are already aware of the things that the professor discusses though. Sure does open your eyes on what made everquest and all those evil games so much fun to play. 