But there's a lot being swept under the rug in saying, "These are (usually pretty minor) technical challenges, and I haven't heard one yet that we won't be able to overcome with today's technology." It comes close to a "sufficiently advanced compiler" or "just an implementation question."
Autocars are going to be held to a much higher standard than human drivers. This sucks, is irrational, and is unfair, but thems the breaks. Given that media and social environment, a single fatal car crash will cause a firestorm that could delay widespread introduction of driverless cars for years. People are terrified of new technology: see the shit show about a Tesla catching on fire, or the people who think people wearing Google Glass deserve to get assaulted.
We absolutely have to tread carefully here.