It's amusing that Eric Schmidt is the challenger on http://www.longbets.org/4 in light of Google's autonomous cars.
I'm just hoping that in 80 years I won't be alive to see my comment becoming horribly wrong, with people laughing at it while a processor flies them across the world.
Consider Captain Sully's recent decisions in just such an emergency.
You're right: building an automatic car is much harder. It's counterintuitive, but speed or altitude are irrelevant if the problem space is sufficiently simple. Additionally, risk doesn't scale linearly. If a plane crashes at 800km/h, all people on board will die; if a car crashes at 130km/h, you'll see a very similar result.
If a car when parking is out by 1% it's maybe sticking out of the space and causes other people to have to park badly too, if a plane rounds incorrectly or a sensor plays up and is 1degree out (so even less than 1%) it lands onto of a terminal filled with tourists.
Even as a professional programmer I tend to trust unknown programmers less and less, bugs get uncovered too late, shortcuts taken... online e-commerce fine, cars and busses - maybe but scaling up the trust and risk involved is difficult.
http://en.wikipedia.org/wiki/Buran_%28spacecraft%29
So, the technology to do these kinds of things has already been done before (though unfortunately neglected!). I think the main challenge is just convincing people that it's safe enough that they will be willing to buy tickets.