RFID applications has been increasing and used for tracking luggages, trucking, lot msnufacturing, containers, parking lots. And even in banknotes? It seems the Euro and Yen central bank authorities did consider using RFID in banknotes but for bigger denominations like Euro 500 bill or Yen 10,000 banknote for cost reasons of course.

It is said each RFID chip costs about 20cents and not cheap for small denominations. One of main reason central banks consider RFID in banknotes is anti-forgery, to make life more difficult for counterfeit. On the other hand, there's the privacy issue. With RFID in banknote, they can literally 'follow the money', track my spending habits, travelling, eating!

Two interesting articles about RFID in banknotes here and here