I've owned many different smartphones, never an iPhone though. I've noticed that a LOT of iphones have had the glass break, and it seems to be far, far, far, far, far, far, far, far, far etc. More common among iphone users than among users of other smartphones. I myself have never broken any of my smartphones that way, so I wonder why it happens to so many iphone users?
Also I do not accept the theory that more iphones than other smartphones are the cause, cause the numbers are just way out of proportion for that to work.