Overheating problems with your Apple iPhone? There are some reports on the web that indicate some handsets may well be affected. Problems stem from the back of the phone getting warm, and can include discolouration.
The same problem has appeared with the iPhone 3G, and also the T-Mobile G1. The iPhone 3GS becomes very very hot, not only on the back but the whole of the front face as well. The phone was to hot to put against the face or any other part of the body, but surprisingly no discolouration was to be seen on the phone although this was a black handset.
The phone at the time of over heating (or getting very hot) was browsing the internet and using a game. Is this a one off isolated issue, or is it a sign of something bigger.
source - PC World
I shot a 15minute video on the weekend and the phone got Hot, the front face up near the ear piece was very uncomfortable to touch. I suspect if I had shot for 30 minutes there would have been trouble.
My iPhone was surprisingly warm, not hot enough to discolor the back though.