DRM is draconian technology implemented into software to "protect" it from piracy. In actuality, all it does is punish the consumer who legally purchased the game and causes frustration. There have even been times where I find myself purposefully pirating a game so that I won't have to deal with DRM and it's inherent problems. I think a good example of a DRM free PC game is Sins of a Solar Empire by Stardock. They created a very popular RTS game sans the DRM and have managed to make a profit. They're business model is the epitome of what all developers should do. They create a game with the intention of making it so good that a consumer will decide to buy it instead of pirate it because they like it so much. .
FTC Town Hall to Address Digital Rights Management Technologies - Event Takes Place Wednesday, March 25, 2009, in Seattle #539814-00298
FTC Town Hall to Address Digital Rights Management Technologies - Event Takes Place Wednesday, March 25, 2009, in Seattle