As a private pilot, I never shut my phone off in
my plane, but on an airline I do it because its easier than arguing with the flight attendants not to mention the rules, I don't have to agree or like them but I could still get black listed from that airline. One thing about using a cell phone in a plane at altitude (Private Aircraft not Commercial) is that you get better range, but it can be very sporadic, I assume this is caused by the handoff from cell to cell?
A quick google search turned up this:
(shamelessly copied from
http://www.wisegeek.com/why-cant-you...n-airplane.htm )
In 1991, the Federal Communications Commission (FCC) banned passengers from using their cell phones while on board an airplane that is in flight. The ban was instituted because the FCC suspected that the radio frequency emitted by cell phones could malfunction an airplane's equipment systems. In complying with this rule, different airlines have instituted different policies about when phones can be turned on and off. In 2005, the FCC announced that it might consider lifting the ban on the use of cell phones on airplanes, with certain restrictions.
So it's not the FAA that set the rules but the FCC, who by the way also regulate any wireless device.
The argument that you must turn your cell phones off in hospitals? Have you ever met a doctor that doesn't have a cell phone or a pager (kids pagers were these text only things we had before we had cell phones and texting). I am aware the pagers were receivers only but the radio signals don't only go to the pager or receiver, so they should cause the same issue.
Just my 2 cents worth. I know many commercial pilots both transport and passenger and I can tell you that none of them turn their cell phones off, although they rarely use them.