I dropped my iPhone 4 on concrete and the back glass has a huge crack on it near the camera. The camera and everything else still works but it's just the crack. I bought it in November 2010 and have already had it replaced once a couple of months ago for free. Will they replace or repair it for free?
Cracking the glass, whether front or back, is considered out-of-warranty damage and not covered. You can see if the Apple store genius bar staff are able to replace just the back glass. The out-of-warranty replacement cost for the whole iPhone 4 is $149.