My understanding is that the cell phone ban isn't due to concerns it'll mess with the plane, but rather that it'll mess with the cell systems. When you're on the ground, your phone is only able to "see" a few towers, but up in the air, it can "see" many towers and I've been told that can cause problems with cell switching. I've heard that it's a regulation that came from the FCC, not the FAA.

But that's just what I was told, not sure on the accuracy of it.