This is a real deficiency in any rating system. A one-star review (or a five-star review, either end of the bell curve) should require a short review as to precisely why the user thought the app was so terrible (or so outstanding).

These "reviews" are clearly from people who removed the app and were prompted to rate it by the iPhone OS.

This system really doesn't make sense (you wouldn't remove a great app) and might need to be removed from the OS, or revised.

The OS could for example, prompt the user the nth time an app is launched. But that would probably be annoying.

Or Apple could send an email every now and then to invite users to rate all their apps (or the recently bought) with an easy to use interface, where they can just rate by number of stars (à la Netflix) and possibly add a comment.