I've heard stories of the glass cracking on the iPhone 4 and 4S, but I've never met anyone who had it happen to them. I've never heard the story about an iPhone 5 bending, and it goes without saying that none of my contacts have had it happen to them.
There's no published data on this. If it's going to bother you tremendously, then I'd suggest doing as others have said and getting a case for your phone. Sure, it alters the look and feel, but if you're the type of person to worry about damaging your phone in some form then the peace of mind is worth it. If you get a battery case (such as the Mophie cases) then there's additional functionality that serves as an added bonus.
There's no published data on this. If it's going to bother you tremendously, then I'd suggest doing as others have said and getting a case for your phone. Sure, it alters the look and feel, but if you're the type of person to worry about damaging your phone in some form then the peace of mind is worth it. If you get a battery case (such as the Mophie cases) then there's additional functionality that serves as an added bonus.