Another issue may be whether or not consumers want to be seen in one of Google's self-driving cars.

The vehicles' outlandish appearance doesn't bother me because I'm a long-time advocate of self-driving cars, but it may be an issue for other consumers.

Other car manufacturers such as Cadillac are working toward fully autonomous vehicles that look like stylish, regular cars. The computers and sensors are hidden in a spare tire compartment.

I wonder if Google is underestimating consumers' preference for traditionally good-looking vehicles. I think about how the company was criticized for underestimating the aesthetic roadblocks involved in the Google Glass rollout.