Apple will not replace a bulging battery out of warranty, having gone through 2 apple senior analysts on the phone and a local genius bar, they don't recognize it as a defect. They do recognize that it only happens once in a blue moon, but apparently that isn't a defect, that's normal. The phone analyst did say they may fix it as a one off if you have damage on the machine stemming from the bulging battery, but they offer no guarantee of course. btw, this apparently happens to the new MBP integrated batteries as well and again they may or may not fix your machine out of warranty if the bulging damages circuit boards.