There is also the possibility of "Denial of Service" problems
Exactly. Any time there's a bit of wire between two computing devices, someone, somewhere, has the skill to use one device to access the other, overload the other, corrupt it or otherwise compromise or render it incapable of providing the service it is supposed to provide. You've got to be barking mad to have a wired link between 400 people with their entertainment systems and randomly-hosed PCs, and bits of the aircraft that are trying to do something important. Does make me want to fire up Ethereal and friends the next time I'm on a flight.