"This is the same as any other distraction while driving - you can think about other things than the road while driving legally (work problems, family problems, etc). If you can still safely drive, great. "
Thinking about things doesn't remove your eyes from the road for 20 seconds. Accidents happen because people don't follow the rules of the road. They don't follow the rules because they are looking away from the road for extended periods of time. As far as I know, the laws aren't really enforced yet. There's also been no social push to make it socially unacceptable.
I get into this argument all the time with my libertarian friends. It ends with them saying that we should outlaw cars because they are dangerous. I still contend that cars are safe while people are following the rules. One of the rules is that you need to be paying attention to the road. That doesn't mean your freedom is compromised.
I get pretty worked up because one of my friends was killed by a teenage texting. The worst part is she didn't even know she hit someone, she thought she might have hit a deer. But she hit my friend who was riding his bike, ripped off his leg and he bled out trying to get help.