Besides, almost all of these patents seem to protect the ornamental design rather than the utility. Most people here don't object to patenting the design of cases and the like.

Though I'm now beginning to wonder. Could someone copyright the design of cases and sue for copyright infringement/plagiarism? Or would that open up an even worse can of worms?

That's exactly what's happening between Apple and Samsung in Europe and elsewhere, right now. Apple complains that the Galaxy tablet is physically too similar to the iPad.