Urs Holzle of Google said the following at Structure a couple weeks back: "You don't want to have a self-driving car that depends on an uplink for its driving ability. Vehicle to vehicle communication has to be a plus not a required."

As with detailed maps, other types of information would probably improve the overall safety and reliability of an autonomous vehicle. But, at some level, it needs to be able to drive on its own based on the environment it can directly sense.

That's basically what I was saying uphtread; self-driving cars need to get safe enough in all conditions to replace humans without relying on data broadcasts, but once they reach that point data broadcasts that allow them to identify and avoid situations that are relatively more dangerous and/or improve routing based on dynamic conditions still can have a valuable role.