I'm a londoner and we have here a system of public transport which is controlled by cards ('oyster' cards, RFID credit card sized things - https://en.wikipedia.org/wiki/Oyster_card).
Not exactly to address your point but they're a good way of tracking individuals so I always try to pay anonymously (cash) and never register it. I should probably buy a new one every few months but usually forget.
FYI anyway. Privacy aside it's a pretty decent system.