I've seen it mentioned here, at least a couple of times, that when you can't get a cell signal that text messaging might work. Could someone clarify this for me?

I know that in emergencies, such as in NOLA after Katrina, the cells were jammed with traffic. While voice calls couldn't be completed, text messages were going through because they require very little bandwidth as compared to a voice transmission.

It seems to me that if one cannot communicate with the nearest cell tower for whatever reason (distance, obstruction, it's just plain broke, whatever), your text message isn't going through either.