Re: @Dave 126
I would expect that the number of times a human has to suddenly jump in to ensure safety is VERY low, otherwise it would not be deemed safe for use. I'd love to see information too, but I think we're all underestimating how smart the car is in the same way we stereotype computer speech recognition as being the way it was in the 90s.
I would not be too surprised if this is Google's 2nd "big product" after Google Search in terms of revenue.