Assuming this is true, it would seem that even good, old fashioned, paper currency doesn't provide the level of anonymity that one would think. Scary...
Hasn't really provided it for quite a while, as long as there's an infrastructure to track serial numbers (you've presumably noticed that each bill a unique serial number, except for counterfeits and maybe printing glitches.) It's quite possible to record the serial numbers of bills before distributing them in applications such as ransom payments or drug-buying stings, and wouldn't be too hard, with current scanning technology, to track them at banks, tax offices, etc. (Of course, neither AT&T GIS (aka NCR) nor Diebold currently makes ATMs with serial-number scanners in them, but it wouldn't be hard to require banks to scan the bills before filling the cash machines.) During one of the "Government's going to replace our Real American Greenbacks with Pink(o) Money" scares before the plastic-strip money arrived, USA Today had an article in their money section showing dollar bills with bar-codes instead of the Arabic-numeral serial number. Bill