Multiple cases of iPhone’s overheating and the battery of the phone quickly depleting have been causing iPhone users 
problems recently. Most believe it’s down to the software, the 3.0 firmware that Apple released a few weeks ago as it only seems now that users are having these problems.
Apple blame the overheating on the hot weather and are blaming people for leaving there iPhone’s in hot places but the battery issues must be in some way connected to the new firmware as I experienced today.
My iPhone 3G which used to run 2.2.1 would run under moderate use each day without getting into the 20% battery area, with heavy usage it would get down quicker and I would have to charge. But today whilst at a friends house I decided to do some live streaming using Qik, however after about 10 minutes I noticed that my iPhone had heated up considerably and the battery had lost maybe 30/40% of it’s charge. Now I know for a fact this isn’t usual as I’ve used Qik before and the phone didn’t have the same problems using 2.2.1.
It seems that there must be something not quite right with the 3.0 firmware which is causing maybe the CPU to be overused, causing the phone to heat up or something in some setting which isn’t coded properly and causing these problems.
I’d be interested to try out the 3.1 Beta to see if it had the same issues, however I’m not currently a developer so can’t try it but if anyone has tried it leave a comment about if you experience the same issues.
Sam's Blog 
I have the same problem. I also did not have it until 3.0 and not even as soon as I got 3.0… Just started a couple days ago and I have changed NOTHING in the way I operate the phone. I DO have a developers account and I will be trying 3.1 later today.
Just had same experience while hooked on my belt attending an opera. Almost too hot to touch and 30% drain in an hour, in airplane and silent mode. Had to turn off completely.
Could it have something to do with the 3MP camera application that was running when I turned off the display?? Brand new phone last week. WTF??
It could have been as I have experienced that but I’m not sure why it would keep the camera running, I mean with most app’s it just closes it then once you unlock the phone it re-opens it and your back where you left off.
I might test this and run some tests with the camera app running against just the normal springboard running.