Blizzard already has built in cheats in single player. You just press enter and type a few phrases. However the built-in cheats disable achievements when activated.
This is key. If they didn't strike out against this kind of cheating then people wouldn't take any of the achievements seriously and the replay value of the game would be diminished.
Indeed. To further show the pointlessness of this kind of cheating, achievements are not available in single player mode, but only on battle.net (apart from the campaign-related ones).
