I accept 1, but 2 is debatable, we need to encourage people to NOT fuck around with gadgets in the car at all.
Not gonna happen.
I cant imagine how bad my current car, a 2002 Nissan Silvia would be if I couldn't swap out the stereo with something that knew what an MP3 was.
That depends on whether it has a changer interface, and whether you have a changer. I have a 1997 Audi A8 with a Bose stereo with no aux input, but I can get one by slicing into the CD changer wiring and using a switch and/or relays (I have the 12V audio signal relays already, have been too busy to make the mod though) to insert my own audio source in between. Or an el cheapo (~$10) panel-mount mp3 player/bluetooth receiver from dealextreme has a line input, so it's just a matter of finding some connectors which fit the board or soldering on some leads, and making a quick splice. Got a voltage regulator so it can run on 5-32V or something ridiculous like that. I might just go that route because there will be no relays to go bad ever. If the thing goes tits up it'll be easy to splice it away.