My iPhone does get hot, but not so hot I can't pick it up -- usually when I'm running 3D for a longer stretch of time or when the phone is doing some serious calculating like audio or photo editing, I start to feel the heat coming off the back. Batteries are to blame for some of the more extreme problems, however, and that's not a huge surprise, given that batteries in any mobile device have their issues. The good news in that case, however, is that the phone is unlikely to actually explode -- the repair guy Wired talks to says that "a little bit of smoke eventually is probably the best bet." Not that a smoking iPhone is a good situation at all, but you can at least be sure that your iPhone is not quite as hot as the fire under your burgers this weekend.
[* Note that the Apple KB article referenced here about temperature warnings/"don't leave the iPhone in the glove compartment" for the iPhone 3G and 3GS is not a new post, nor is the temperature alert screen unique to the 3GS; the KB was simply updated to include the newer device. Jim Dalrymple at The Loop has a solid rundown. FoxNews incorrectly reported that the support article was specific to the 3GS, but then did cite PC World's Melissa Perenson and David Coursey with personal stories of wicked-hot 3GS units. If your 3GS is overheating, check in with Apple support or your local AT&T store. -Ed.]