Until recently the taxi cab business in virtually every city in the country functioned like a medieval guild. And as Adam Smith might have predicted, we consumers are worse off for it. But for me at least, things have changed. Say I need a ride to the airport. I can tap an icon on my cellphone and a car will arrive, usually within five minutes. I normally take whatever vehicle is available; and that's most likely a black town car. But if I have several passengers with me and we have a lot of luggage, I can order a van....