As mentioned in a prior post, the “no cell phones” is an FCC issue and has to do with how many cell towers you’ll tie up when calling from 35,000 feet, which annoys the heck out of the cellphone companies. Those “cellphones” mounted in airplanes (and available for private sale for much money) do not have this effect. It’s not a safety issue of the cellphone screwing up the electronics in the plane (although that is a very remote possibility) and in a dire emergency they can and have been used.
As for the rest of the electronic toys people carry these days… in aviation, if it isn’t proved to be safe it’s assumed to be unsafe and is therefore usually forbidden. There are devices (handheld aviation transceivers, scanners, GPS units…) that are intended for use in an airplane and are presumably safe, yet you many still be asked to put them away. This has to do with airlines having control over what happens in the passenger cabins, and because a blanket ban makes for an easier and quicker routine for the staff who do not have to inspect each and every item but simply tell you “put it away”.
I’m not sure about the person who thinks that passengers listening in on the pilots might cause a problem. The pilots aren’t doing anything secret up there - heck, they’re being recorded by the CVR and any communications with air traffic control are also recorded in the tower. A number of airlines have an audio feed that let’s you listen to the cockpit conversation through the same headphones you use for the movie.
As also mentioned, the safety issue is very important. Not only would a walkman interfere with your hearing of verbal instructions, but such an item could be a dangrous item of flying debris in the event of a crash. If something goes wrong on take off or landing it will probably go wrong very very very very quickly. You may not have time to take off the headset and go “Huh? Whudja say? Could you repeat that?”. Now, if you don’t mind the idea of crawling around a smoke-filled airplane with a chunk of walkman embedded in your skull, having missed the one-time-only announcement of which way to go to get out just keep rockin’ to the latest CD.
Actually, you might consider the rules in a commercial airliner liberal compared to the ones I impose on my passengers in small planes. In my airplane, not only will your walkman/other device be turned off and stowed, you will also be required to sit still and keep quiet though take off, and again from about five miles out through landing and until we are off the runway. En route while in cruise you may listen to music, tell jokes, or even chairdance - I don’t care, have a good time. It all comes down to safety - take off and landing are very demanding phases of flight. I have had to abort both take offs and landings and have done so safely becuase I pay attention to what’s happening outside the cockpit. That’s much easier with minimal distractions inside the airplane.
This does crank my handle - folks, a lot of the rules in aviation are there because someone was seriously hurt or died in the past and are intended to keep Bad Things at a minimum. Even if it seems silly or senseless to you, please follow the rules - they really aren’t there to torture you but usually for your own safety.