Autopilot will only work if all vehicles have autopilot and they are registering their paths. This is why Airplane flights are highly regulated. It is to avoid one plane flying through the path of another.
We are no where near that on the streets yet.
Don't think we ever will be considering the number of cars on the road and the small size of total square miles of road available versus the number of planes in the sky and the spacious cubic miles of atmosphere available to them.
Of course this is the car maker's fault, they built it.
If Tesla made an error here it was in calling their system "Autopilot". No matter how many warnings you issue, the name still suggests a hands-off control system.
Driver did not have his hands on the steering wheel.
It is their fault.
end of discussion.
You know, this brings up an interesting debate.
I am certain there is a law on the books in just about every state that says something to the effect of "a driver must be in control of their vehicle at all times." Now how that is worded will be important in a case like this.
Right now autonomous driving cars are so new the laws currently on the books probably do not address them...of course there could be some laws out there that by the very way they are worded could possibly be interpreted to cover such vehicles but I doubt they would be very specific. Thus from a criminal standpoint, the car itself would not be to "blame" for contributing to the accident as the driver of that car, by law, should have always been in control of that vehicle...in theory.
On the civil side though, I do believe the family of the Tesla Driver would have a case. Like John mentions, the fact that Tesla refers to the feature as "autopilot" could be interpreted to mean that no active supervision of the controls are necessary and thus be somewhat liable for damages.
On the other hand, Tesla is very up front that while the car can "drive itself" this doesn't mean the driver can take a nap and enjoy the ride. They specify that the driver must retain attention at all times. IIRC, even with aircraft autopilot systems a pilot must be at the controls at all times monitoring what is happening around him so that he can instantly take over control of the aircraft if something goes wrong. Ergo even though the system is referred to as an "Autopilot" system, that...in and of itself...doesn't necessarily mean that the driver need not continue monitoring or take action while the system is in control of the vehicle.
I am certain this will go to the courts and it will be a major factor in the future of autonomous vehicles.