Originally posted by Arjay Bee ...didn't quite fit and didn't quite protect the bits that were most prone to damage such as apex of the prism cover LCD screens and allowed dust and crud to build up between body and cover...
I'll agree with this.
I'd compare this to most cell phone cases but the big difference is that a silicone case for a phone will provide adequate protection if it accidentally falls off my lap or takes a tumble down a flight of stairs. A rubber cover wouldn't do much to protect a camera since the screen and lens aren't covered, and the magnesium body is strong enough that a silicone cover will only really help in preventing some cosmetic scratches.
With that said, over time I accumulate a decent amount of dust and pocket lint between my case and my phone. After a while the dust trapped in the case rubs against the phone and caused dull spots or marks that won't clean off or shine up and in my opinion look worse than a few light scratches or dings would. I deal with it since I'd have a cracked screen by now without a case, but if I were to resell the phone it would detract from the value. I think the same could happen with a heavily used camera covered in a protective rubber skin, and that would annoy me much more than with my phone.
Moral of the story - I pay attention to my camera and try to take care of it, but I take comfort in knowing that Pentax has designed my camera rugged enough to take a beating if I slip up.