It's all academic to me. I've been advised to both leave the nut off and to be sure to screw it down but so far I've only lived .8 of a lifetime so I've never even known anyone who has had this problem happen. I do know, however, that if I screw that nut down tight before I put the tire on, there isn't enough room to fit the tire around the tube properly. If screwing the nut down can be part of the problem when a tire slips, then what is the point in them in the first place?