|Internet acess and DVD players can be put in the back seats lower enough for anyone outside of the car not to see the movie and get distracted, and be capable of putting head phones to them. That way a driver would not get distracted by the sounds of the movie.
I agree with putting them lower, however, this would hamper the vision of anyone riding in the very back seat of a mini-van or whatever. I asked my boyfriend (he is the service manager at one of the car dealerships in town) about the positions of these things and why they are placed in the ceiling and his answer was: better storage, out of the way, kids would kick them if they were mounted any lower. It is also more accessible should one become damaged or need repair if it is installed from the ceiling.
Tinting the windows won't do the trick either since whenever there is a light inside a vehicle, the tint isnt effective. It might damper the vision of other people around them, but would still give others a good idea of what is being watched.
I personally wouldnt want my kids to see anything of this, but as I see it, that person and what they are doing is not really any of my business. Since watching porn isnt illegal and DVD's in cars arent illegal there isnt a whole lot that can be done. I dont agree with it, but it isnt my place to tell someone what they can and cant do in their own cars or houses for that matter, especially if it isnt illegal.