This comes as quite a surprise to me; I didn't register a prediction (I have no idea why, maybe I just missed it), but my prediction would have been like those in http://predictionbook.com/predictions/2750 - only in the 20s or 30s%.
Yeah, as one of the people who put this at only 20% I'm glad I did. I was originally going to put around 95% against, and then I thought that might be overconfidence. So now I only look somewhat silly.
http://blogs.forbes.com/alexknapp/2011/06/22/nevada-passes-law-authorizing-driverless-cars/
http://news.ycombinator.com/item?id=2688424