So, in essence, your friend has a malfunctioning phone.
How many iPhone 3GS devices are out there now? Over a million? Given that some portion of the stock will be defective, let's say one in every few thousand, you're going to have hundreds or thousands of devices with major problems.
From the symptoms described above and in the article, it sounds like some combination of software and hardware is causing these phones to burn through battery power at an alarming rate. Ok, fine. So tell your friend to take it to a Genius Bar and let us know if Apple states that this overheating is expected behavior.
Given all that Apple is stuffing into these devices, I'm surprised they work so well for the vast majority of users.
- written from an iPhone 3GS