I see no reason why phones should not be banned from the cabin or at least handed over to the airline for safe keeping during the trip - no one is that important that they have the right to risk others lives for their delusions of grandeur.
I hope that anyone caught using them gets banged away big tiime - it only needs a few to get punished before the rest get the message.
There are times when it is an accident. A chap in China inadvertantly left it on and the planes intsruments went 30 degrees out. I think it was a genuine oversight in this case as he was not using it. If the phone wasn't allowed in the cabin in the first place this may not have caused such a problem.
Incidently what would happen if the phone was in the hold but left on?
It may be better to have them handed over to the airline for safe keeping during the trip and handed back afterwards - with legislation to lock the errant ones away if they refuse or "forget" to hand them over.