In Florida we have a huge toll system with the majority of it under an RFID like 'pass' you stick under your window. Tolls are ran by the state, largely on busy state roads in larger metro areas. I'm a pretty big fan, largely because it contributes to our lack of a state income tax.
My mind immediately went to the privacy implications of that. But then, you are in public on a public road so maybe tracking cars isn't such a big deal.
