I bought the iPhone 5 two weeks ago, this is my first iPhone and I gotta say - I'm not exactly thrilled with my experience right now. I had the same issue; put my phone in the small pocket of my purse and it bent in the top, left hand corner of the phone. I didn't drop the phone, or the purse. The phone is showing a very noticeable crack near one of the volume buttons.
Apple won't help me in store, or via their 1-800 number. I am being told I have to pay $200 if I want to replace it since this apparently looks like it was a user issue and is not a manufacturing issue. After seeing multiple comments on web forums, it is quite clear we did not all do this to our phones. If I had dropped the phone with enough force to bend it back like that, it seems to me the screen would also have damage.
Clearly the metal used with this model is more malleable than it's predecessors. It is not reinforced enough around the volume buttons causing it to bend backwards if any force is put on it over a long enough period of time. No one should have to be paranoid that their $700 phone will warp when they put it in their pocket or purse. Apple needs to realize this is a growing issue, fix it, and show us that "world-class" customer service they are supposedly known for. I have yet to see it.