This guy runs down a list of things that are unsolved and really fucking hard:
https://www.youtube.com/watch?v=x5CZmlaMNCs#t=94
With self-driving cars, new infrastructures need to be built, not for human, but for different censors mounted on the car.
DARPA and massive state intervention in the economy should be right up there alongside private entrepreneurs like Musk who complete the last mile of bringing tech to market. It just kills me that there can even be a thing called a "Silicon Valley Libertarian" who's against "big" government. SV is a product of government investment.
John Leonard puts tremendous passion into the subject, has done amazing things and talks about how hard this stuff is.
Thanks