It seems to me that there are two issues here. Maybe more, but two general categories. The first is engineering. Can such electronics interfere with the navigation or communications systems in an airplane (not just 787's but any aircraft operating under Part 135 or 121)? If so, then what kinds of electronics? Can they be categorized (e.g., things that transmit -- to include devices which poll or search for outside links)? Can the list be further refined and defined so that a list of potentially harmful devices is possible? Before I go on to the second category, a little anecdote. Like many government employees, I have to carry around a blackberry. Newer, but not the most current version. At night, I used to have it plugged into the charger on my sink. No more. When it RECEIVES a message (not sending a message) it turns on my electric razor! (Yes, I know that the way it is designed, it automotically sends out a transmit signal when receiving a message.) Move it a few feet away and the effect disappears (radiation dissipating by the square of the distance.) Still, it is enough that I make absolutely sure that the device is turned off in a plane, whether mine or commercial. Just an anecdote which may not be repeatable on Mythbusters.
The second is a human factors issue. If you found that some devices did cause interference and not others, or that undamaged devices were fine but devices with cracked cases or what not could cause interference, how realistic is it to believe that the passengers are willing or even able to discriminate in their use of such devices (or even flight attendants to keep up on the list.) There is also a safety issue. Someone plugged into a game or music or whatever is not listening to the safety instructions and may be completely unaware that there may be anything wrong with the airplane...say, requiring an emergency evacuation. You could say that it would just be Darwin in action, but in a crowded airplane, that can affect the lives of others, too. (Just look at people WALKING on the street, totally oblivious to everything around them...including red lights, cars, and other people.) Overall, it may be best just to restrict everyone from using such devices in critical stages of flight. What you do on your own airplane under your responsibility as PIC is up to you.
Remember, we are dealing with the same people who pressured the TSA into reinstating the restriction on pocket knives of any size (requiring me to return to using my teeth to open the hermetically sealed plastic eating utensils.)