Actually, I don't believe cell phones pose a risk to flight safety due to electromagnetic interference. I've spoken with many experts in radiofrequency who tell me that the signal strength is just not strong enough to affect shielded avionics. I personally have never experienced any incidents of interference. Also, apparently Boeing did quite a few tests to try to reproduce problems reported by flight crews and weren't able to reproduce anything:
http://www.boeing.com/commercial/aer..._textonly.html
However, I still believe in a total ban on cell phones in flight. I believe they pose a serious danger to flight safety for the following reason. If you have hundreds of passengers talking on cell phones, screaming above the engine noise, it will create an enormously stressful environment for the cabin crew and passengers. This will significantly increase the risk of incidents of violence. Also, cabin crew and passengers will be much less effective in responding to any emergency, such as an evacuation, in such an environment.
So, I say let's keep the ban...