My 2 1/2 year old iPhone 5 recently developed an issue where part of the touchscreen glass was no longer flush with the bezel--i.e., part of the the glass had popped up. As my phone was 1.5+ years out of warranty, I was pretty much resigned to the fact that any repair/replacement to correct this issue was gonna cost me money, but having read stories about how Apple sometimes offers goodwill repair or replacement, I took my chances and scheduled a Genius Bar appointment. Fast-forward to my visit, the Genius took a look at my phone and without hesitation or asking me any more fact-finding questions, replaced it with a refurbed phone!
As to what caused the glass to pop up--the battery apparently swelled up; I'm guessing that this issue may be infrequent but not completely unknown since after all, Apple replaced my way out of warranty phone for free, other than of course taking my old phone in return. Google search also reveals similar stories of the glass popping up due to the battery expanding. And before folks start offering that my battery swelled up due to my perhaps using a non-Apple approved charger--all of my chargers capable of charging my iPhone are either Apple-branded or Apple MFI approved...but even then that's a moot point since Apple replaced my phone for free anyway.