I just had a though on the glass back after reading all the posts of broken glass on the back. Previous generations saw large numbers of returns in the warranty period for defective internal/electronic hardware components. After the return, apple started noticing that a lot of the problems were a result of blunt force trauma. There was no real similar detector for impact like there was for water damage. So apple designed it so that if you drop your phone with sufficient force to potentially damage the electronics, it would be evident to a Genius in the form of a cracked or shattered glass panel. Just a theory. I like the glass. I don't think there is evidence yet to show that more backs are breaking now than screens did before, but more backs are breaking now than backs did before, that is for sure.