recording of your face during all transactions + receipts would roughly duplicate the card-level tracking. Most paper money has a serial number that could be t

recording of your face during all transactions + receipts would roughly duplicate the card-level tracking. Most paper money has a serial number that could be tracked for following the chain-of-possession for that piece of paper. In the case of Germany I can see a law being written that would require serial numbers be recorded for person-to-person cash exchange. Those guys love regulation. :)