The whole cell phone in flight thing has nothing to do with interferenece as jetjock and the myth busters have pointed it. It goes back a decade or so ago, and was put into place by the Federal Communications Commision (I know this because I know the former head of the FCC, here name is Gloria Tristani, look it up if you want, Clinton Admin). Anyways it had to do with cell phone signals hitting various cell phone towers, therefore not allowing the cell phone company to figure out where the call was originating from, and therefor not allowing them to charge roaming and so forth. That was straight from the horses mouth. Think of how many towers you could reach from FL350. It is outdated technology now and therefore probably an outdated law, or reg, whatever you want to call it.
Just my .02c, actually that is more like a whole dollar.