Steam users who purchased keys for Call of Duty: Modern Warfare 2 through what turn out to be grey market sources have found themselves banned from playing the game. Apparently users have been able to buy discounted keys from sources that buy them in bulk for cyber cafes, foreign sales, and similar setups, only to find this is a no-no. A post to the Steam Users' Forums by Valve's BurtonJ says: "If you purchased just a cd key for the game then you purchased from an illegitimate seller and the game has been revoked." In a later post he clarifies: "I am sorry but you all did not purchase from a legitimate retailer. It is recommended that you contact the seller to request a refund. In the future, you should only buy unopened retail boxed copies from legitimate retailers or purchase via legitimate digital download services such as Steam and Direct2Drive." We saw a note about this yesterday with no working links to evidence of this, but found the sources today courtesy of a post on Voodoo Extreme.