A while ago, I read on sheldon's site that some bikes had "cups" for the QR, so that if you accidentally left it unlatched, the wheel would not fall out. "That's the stupidest thing ever!" I thought, for who would possibly leave their wheel un-clamped? Really, what kind of moron could ride 5 miles before realizing he didn't lock his wheel in, and only noticing then because there was excessive wobble when he mashed the pedals, leading him to believe he had broken ANOTHER axle?
On a completely unrelated note , my commuter has these "cups", and I think they're a darn good idea. You know, just in case.