If the FAA didn't prohibit the use of a Cel phone on board, the FCC would.

From 30,000ft you can hit hundreds of cel towers line of sight, which can seriously mess up/confuse/overload the cel infrastructure. When there's a local microcel on the aircraft, your cel phone scales back transmit power (to talk to it only), and doesn't interfere with the rest of the cel network.

As for interference from equipment, yes they do cause some small amount of interference; not enough to cause trouble to an aircraft, but 100 of them might be enough. Plus you should be paying attention to what's going on taking off and landing as statistically there are the most dangerous parts of a flight.

Please don't be the kind of person that caused a JetBlue flight attendant to lose it; there is logic behind the reasons; and you know what; your phone call can wait.