An article on preventing cheating in chess and how computers and statistics come together to assess likely outcomes. This is the primary way that cheating is detected in online poker and how several people at 2+2 have uncovered whether or not certain players were cheating. The reality in the poker world is that most sites and players are legitimate, but a few bad apples spoil perceptions.
http://www.nytimes.com/2012/03/20/science/a-computer-program-to-detect-possible-cheating-in-chess.html