That should give you a clue about how cell phone use would be on an aircraft with a captive audience who often are not able to get up because the seat belt sign is on for safety or "homeland security" reasons (I was on a 2.5 hour flight that had maybe 15 minutes of 'walk-around' time not too long ago). It would be very annoying to sit by some of the people I have sat by who can not and do not remove the phone from their head unless strongly ordered to and have no concept of voice level modulation. I suspect there would be a few violent acts on those people after about an hour.
And yes, as some folks have pointed out, there are those who think rules are meant for others and say "f you" (they do seem to love cussing) if you try to point out the rules while they stealth use their RF devices. Hate to see what they would do if it was legal.