I'm not sure that I completly buy the whole "electronics may interfere with the aircrafts navigation/communication equipment". Do you really think if electronics could cause any harm or malfunctions they would allow them? They just trust us the we will turn them off?

You can't bring on a bottle of water but you can bring on a cell phone that may interfere w/ the airplanes electronics as long as you shut it off.
I think they want to make sure that people are not distracted incase of an emergency, so that they can give out instructions and are sure that everyone will here them and know what is going on and what to do. When I was younger I can't remember how many times I've thrown my cell in my bag in the overhead and forgot that it was on. Never had a problem.