Sounds good as far as recognizing the importance of incentive. But I think it has some drawbacks (at least to me):
- I'm always skeptical of forcing students how they should study. Just because you're active in class doesn't mean you grasp the course well. (I recall my fellow students who never spoke a word in class ended up magna cum laude -- while some who were talkative -- too active you lost your concentration -- flunked their exams).
- This whole thing of distributing cards break my concentration in teaching. The books are thick already -- I don't really have much time playing the card game. And it's not easy to make fair decision in split second, e.g. when you see three hands at the same time. Not to mention the sudden protests like "I think my comment is good and deserves a blue. Why green, Sir?" -- you need at least 3 minutes to settle on that.
OK, I'll think about a better system next time. You have an idea? (Some time ago, when Tyler Cowen asked how to solve the RSVP problem, I offer an idea -- that kind of idea: like some machine does all that card distribution thing for me, while I can concentrate with my powerpoints).