I've recently run across several articles/blogs discussing the down-side to gamification. Before experiencing a gamified class myself, I probably would have not given these posts as much merit as I do today. Instead I'm finding I resonate with what they have to say.
Kathy Sierra, a well-known tech writer, had a few things to say about gamification. She categorized situations as to the level of harm gamification could cause. Her cautions make sense to me, and bring back to mind all the reasons I learned it was psychologically inappropriate to always give students extrinsic rewards for their work. While it's not so harmful in some instances, in others it sets up a pattern of expectations that can never be maintained for a lifetime.