I was stuck in traffic yesterday, which I didn’t really mind because I have a fun little yellow convertible, and I was thinking about Uber ($17 billion! – that’s the company’s valuation, not the price of a ride) and Google’s driverless cars (development cost unknown), and I decided it was time to connect the dots: once a car learns to drive, there’s no need to own it and there’s no need for a driver. That’s because the car can come when called, take you to your destination, then go off and pick up someone else. That sounds great and I’m hardly the first to connect those particular dots, but there’s a corollary that seems to have gone largely (though