The fact that the aircraft is EMC tight when made does not mean that it stays that way as cables move, shielding abrades, and even connectors get some corrosion. A particularly evil case is with avionics bays below galleys or lavatories: without EMC, there can be enough problems - look at the AAIB reports. Add EMC possibilities to the mix and the results are not readily predictable.
The business about lap tops etc flying in the event of a crash - how about a YMMM incidence? - is so obvious. Ironically, it's because air and train travel is comparatively so safe that people are not aware of the possibilities.
Incidentally, what is the maximum decelerating g force that the seats will stand without coming adrift and crushing you?