The Associated Press article about the California Department of Motor Vehicles proposed new rules for cars with autonomous driving features[1] suggests one reason to be pessimistic about the vision of rentable self-driving cars becoming a reality as soon as Google would like. (I would like it to be a reality soon, too, but I have to wait for what the technologists and regulators involved can do together to make that a reality for me.) A company that rents out rides to paying riders has to have a market to operate in, and any state could (and, if California is an example, maybe would) regulate that company in ways that might not make it a feasible business. A follow-up article on this news[2] says that Google is "disappointed" by the newly announced California rules.
[1] "California: Self-driving cars must have driver behind wheel under DMV proposed rules" (16 December 2015)
[1] "California: Self-driving cars must have driver behind wheel under DMV proposed rules" (16 December 2015)
http://www.mercurynews.com/business/ci_29262037/california-s...
[2] "Google 'disappointed' by proposed restrictions on driverless cars" (16 December 2015)
http://www.usatoday.com/story/tech/news/2015/12/16/google-di...