Google's experiment to build a self-driving Toyota Prius has already logged hundreds of thousands of miles with only one known fender bender. To tout its potential, Google put a legally blind man behind the wheel and filmed the quotidian yet touching results shown above. What we still don't know is: Who would have been responsible if something had gone wrong?

There's no denying the impact of the video, or the idea that a self-driving car could aid people -- like driver/rider Steve Mahan -- whose mobility has been curbed by disability regain a portion of freedom. Several automakers and parts suppliers, including Volkswagen, General Motors and Continental, have experiments underway to automate some driving scenarios, to research how it could improve safety and fuel economy.

But there's a few things not noted in Google's push, starting with the phrase "self-driving." The Prius used by Google doesn't pick its own locations, and it still needs a human operator; even in Nevada, which has approved self-driving cars for the street, two people must be inside the car at all times, one of which can take control in emergencies. (Google says Mahan's drive was "carefully programmed.")

While technology has advanced, many basic questions remain unanswered, and most experts say any builder of an autonomous vehicle sold to the public could face a massive amount of legal liabilities. With federal agencies arguing that driver distraction poses such a threat that cellphones and moving navigation screens should be limited, a self-driving car would be the ultimate proof of driver distraction. Any good traffic lawyer filing suit after a crash with a self-driving vehicle would immediately use its presence as proof that the owner's habits ran to ignoring the road -- whether the system was on or not. And the web of radar and sensors used in all self-driving experiments remains far from foolproof.

Still, it looked like a good taco.