Has anyone realized that the technology to track the flow of cash currency to individuals is at hand? It dawned on me, as I was depositing 800 dollars at one of the new ATM's that accepts deposits of stacks of cash with no deposit slip required. It would only take a few lines of code for optical character recognition to note the serial numbers of all the cash you deposit. The same applies to cash you receive from the ATM. It also applies to cash you receive as change from the supermarket, pharmacy, barbershop,…whatever.
The upshot is that cash transactions will no longer be anonymous. If you give cash for illicit purchases, (such as Marijuana, or prostitution) and the cash is intercepted, the serial numbers could be run to find the clientele.