I think they come with different problems and can help add redundancy to data input. I would be scared to sit in a self-driving car that depends only on visibility of lines at the edge of the road. However, if there are enough data points available to the car at all points in time, then it makes the probability of failure low enough.

Imagine a system that munches visual clues + RADAR/LIDAR data + Microwave or RF transmitters embedded in the road + GPS/SATNAV + data from other cars via local mesh network. Now, that I'd think about trusting a little bit. Also, I'd definitely be watching 007 movies while my car drives me :-)