Recent "conventional" gasoline-based cars are also full of embedded software, much of it of dubious quality. Consider, for instance, this audit of the software in recent Toyotas, which found bugs that could cause the car to go out of control: http://www.edn.com/design/automotive/4423428/Toyota-s-killer...

What may be unique about Tesla is the explicit provision for over-the-air software updates. But anyone with sufficient technical knowledge and physical access to a conventional car can do very nasty things to the electronics (i.e., deadly to the occupants).