There will be a period of time, who knows how long, where it will be a wonderful time to be a driver. You get all of the pay for being a driver, but you don't actually do any work, as the car will drive itself, but it will still be legally required to have a person who can ultimately take control of the vehicle.
EDIT: Also, law enforcement/cities will hate these things, as revenues from speeding/parking tickets will plummet.