I remember reading a few articles concerning electronic equipment on aircraft a few years ago, and If I remember correctly, the main culprit is not RF based as much as EM. I'm definitely not an electronic whiz (far from it - when I cut a wire I tie the ends together so the electricity doesn't leak out) but the articles talked about the magnetic field generated by electric and electronic devices when turned on. These magnetic fields can interact (say two laptops are turned on and are in close proximity, two or three gameboys, etc.) and can nulify each other or amplify each other causing 2IM, 3IM interference and the like. The magnetic fields can then infringe on the fields generated not so much from the instruments, antennas, etc., but the cabling between the two, which usually runs much closer to the cabin.
The articles talked about the lack of adequate shielding of most consumer electronic devices causing all of this, and since it's a real impossibility to test all devices in every combination, we have the restrictions currently in place. Concerning laptops, the articles did say that most of them do have shielding built in, thus they are allowed where simple toys are not.