So if the car crashes, who is liable - the person in the car or Google?
The person. You can take control of the car at any time, and in case of a crash that the computer can't avoid, you should.
that's why these will never be mainstream in our lifetime. no car manufacturer will want to be help accountable.
Nevada's made them legal. Presumably, Google would be supplying the tech and might be held liable in flaws with the system, but even still, in Nevada the liability lies with the human driver, who has the responsibility to take over should anything go wrong. Baby steps.
The other states don't have anything prohibiting it either, and any legal issues will undoubtedly point to Nevada as precedent. This is real and it's happening right now.
How will they handle adverse weather conditions resulting in skidding on ice, hydroplaning, etc.
Don't many cars already compensate for that? Besides that, Google's tested these things for hundreds of thousands of miles and I'm sure those cases have come up.