[fabian2k]

the Autopilot can't handle certain kinds of situations, and some of them might appear without much warning. One example from accidents that made the news are stationary obstacles like a police car on the side of the road, but still partly on the road. The Autopilot will happily drive into that obstacle without braking. If there is another car in front of you, this might not be visible until you're pretty close. Taking your eyes off the road for a bit might be enough to miss this.

You can't rely on the Autopilot to prevent accidents, it's simply not designed for this. So you have to pay the same amount of attention as if you were driving entirely manually. So if you're doing stuff that would be impossible while driving yourself, you're almost certainly not paying enough attention to the road and are at least negligent. Not sure about US laws, but usually there are laws against driving in a reckless or dangerous fashion, that can catch all kinds of behaviour.