Munchkinism in gaming is also generally connected to zero-sum games, so when gaming against a munchkin you either lose or have to out-munchkin them. The meaning is generally pejorative because more collaborative games tend to become unfun at this point. I've never seen gamers who do odd and massively optimized things that aren't intended for winning zero-sum games, such as building a working CPU in Minecraft, called munchkins. There always seems to be the aspect of outshining the other players within the game in munchkinism.

The analogy of this to the social sphere might be why Tim Ferriss got flak from his 4-Hour Workweek.