I guess it's back to the "some airlines do, some airlines don't" debate now, as I've been able to use my mini disc player on some services, but not others. Not sure why they are banned, but it's probably something to do with pulling the machine apart and using the laser to blind the pilot, or set it to stun to momentarily freeze pax using mobiles.
Talking of mobiles, I flew into JFK a few years back and was absolutely horrified to see a guy a few seats next to me checking his voice mail, while we were still on the glide path! It seems that people tend to think that once the plane is on the ground, it's perfectly acceptable to turn on their phone, get up and start walking and talking and grabbing their "carry on" luggage (read industrial size trolley) from the overhead bins. This is despite the (imho too few repeated) warnings of not doing so. What distresses me most is the attitude of some crew who appear to do nothing, despite seeing what's going on.