As many of you know, I have become a passionate student of gamification. I don't say a passionate advocate, because it is done incorrectly so often (as I discuss in my talk at NYTechUX).
This article from the Wall Street Journal by Farhad Manjoo (of whom I am a big fan) is a good example of the dark side. When it is used to exploit workers, leverages extrinsic motivation, and is used in a controlling manner, it violates all of the factors that good gamification experts warn against. Unfortunately, I think Farhad is right that there will be a lot of implementations like this, at least until the general employer base learns (probably the hard way) that this is NOT what gamification is supposed to be.