Are you a spine breaker? Or a dog-earer? Do you expect to keep your books in pristine condition even after you have read them? Does watching other readers bend the cover all the way round make you flinch or squeal in pain?
I think I'm actually pretty rough with my books. I never bend back the covers because that does make me cringe, but I admit, I'm a dog-earer. I never am responsible enough to have an actual bookmark so I resort to bending the corners. I do that a lot with library books, but if it's a book that I own and value then I'll be a little more careful. It's nice to have your books look well-loved though, right? :P In my mind, a book is meant to be read and loved, even if that does mean it gets a little roughed up and damaged. It only adds character.