I'm sure not anyone will agree with me, but making it mandatory to leave a comment if you rate something 4.5 stars or above would be neat. Personally, I often rate things I really like 4 or 4.5 stars, reserving 5 for pieces I absolutely adore in one way or another. If I rate something 5 stars, I already try to give some positive feedback other then "thing gud Ilik a lot" and even if that's all it ends up being, it's better the nothing I suppose.

Forcing users to leave a comment at those ratings could balance the rating system, making 5 stars more meaningful and stop people from assuming anything less means "I have gripes". Then again, it could also make everyone stop voting 4.5 and 5 stars all together, and everyone will start rating everything 4 instead, which only moves the problem.

Just a thought.