Cell phones should be allowed on planes because there's no serious technological reason why they shouldn't. If airlines want to ban the phones individually, they're more than welcome to, but some may not like it. Phones, contrary to what people imagine, would not be used for talk at a serious level, largely because of how hard it would be to hear.
Cell phones are part of everyday life. Airport screeners and technology have advanced enough to where wireless communications shouldn't affect an airplane's operation, nor should any bombs be brought on board that can be detonated from a wireless device. If there are questions of airplane safety, then each plane should have its own wireless antenna that allows cell phone communications while in flight.