Actually, the agency that banned use of cell phones on aircraft wasn't the Federal Aviation Administration(FAA)- it was the FCC. You're right, they'd hit a whole ton of towers, and in the early days of cell phones, it trashed the way they billed you, and they effectively couldn't.

I have no concrete proof as to this, except that it came from a guy who worked on avionics systems for a few major airlines (including flight testing) that a cell phone has never been proven to interfere with the avionics. When I'm out tooling around in my Piper Warrior, I'll be honest-I leave my phone on.

Not that I have anything fancy enough to get interfered with.... <img src="/images/graemlins/blush.gif" alt="" />
-Kyle