Why does my iPhone 4 get so hot during charging? My iPhone 4 gets hot as the battery is charged. To compound the issue, I think I bought a cheap case that traps heat, which in turn makes the phone even hotter -- you can feel the heat if you hold it in your hand while it is charging. When you stop charging it, the excess heat goes away.

My question is: does this damage the hardware? Also, to reduce the heat, I put the phone on the floor (which is cooler) and I found that the device was not as hot as before (previously I had put the phone to charge on a wooden table). I am unsure as to whether my measure helps in elongating the battery life and protecting the electronic components.
FYI, iPhone 4 does have heat sensors and if it gets dangerously hot it will show a black screen with a yellow warning sign and shut down. It's perfectly reasonable to be concerned and take the measures you have to increase heat dissipation, but batteries warming on charging is quite normal. I wouldn't worry unless the iPhone displays an overheating warning consistently.