Online money tracking

[pianorama]

 Some people now write (discretly) on bills saying something like, "Track this bill at www.cdn-money.com" or "www.whereswilly.com" What happens, is that the person who wants to track the bill, writes the serial number in the website, writes on the bill telling what website to track it on, and spends it, hoping someone will notice the writing, and type in the serial code that shows the original owner where it is and how far it has travelled.
 It currently is legal to write on bank notes, but maybe in the future there will be a law against it for mutilation.