Love it, hate it, or simply not care, iPhone users, at least here in the states, are pretty much bound to AT&T. I won't speak for everyone, but for me, in the Valley of the Sun, this means dropped calls, loss of signal, and failed MMS messages, all while still showing full bars. Granted a lot of these have gotten better since the recent release of 3.1.2 , or the Chi-Town Update as I like to call it (If you're from the midwest you understand).
Better doesn't mean perfect though and I've personally gotten sick of doing hard resets (hold down the sleep/wake & the home button for 10 seconds) to get my calls to go through. Reseting Network Settings seemed to do the trick as well but isn't really any quicker and then you loose all the wifi network information and passwords stored in your phone. What's the answer? It's simpler then you might think, Airplane Mode. As it turns out toggling on Airplane mode for 15 seconds and toggling it back off forces the phone to reset it's cellular calibration and re-lock on to a near by tower. 15 seconds is still a minor annoyance, sure, but it really is minor when considering how much longer the alternatives can take.
*Here's a bonus tip for this week also, this one goes out to all of the parents with youngsters running around out there. As the world changes and iPhone games start being developed for younger and younger children, kids are going to want to play with Mommy and Daddy's phone more and more. An obvious concern here are the accidental phone calls a child might make to China while trying to play with Curious George. An easy solution, turn on that Airplane mode again. Sure it won't stop the most malicious of kids out there trying to make calls but for the innocent ones it poses as an extra level of protection that will work the majority of the time.
**P.S. Wifi can still be turned back on without cellular service being active, important in case the games are online based or if you still need to hear incoming e-mail.