A simple scenario that comes to mind is that given a letter, it's now easier to tie it back to the stamp's point of sale. "Who purchased this stamp?" is a very hard question to answer in their current (essentially fungible) form. Adding barcodes makes this much easier.
This assumes that stamps are scanned when sold, to tie their barcodes to the purchaser. That may happen. It may not. But clearly the more scans a stamp gets increases the tracking resolution for a given piece of mail both after AND before mailing. This "before mailing" part is new and opens the door for a much higher level of surveillance.
This assumes that stamps are scanned when sold, to tie their barcodes to the purchaser. That may happen. It may not. But clearly the more scans a stamp gets increases the tracking resolution for a given piece of mail both after AND before mailing. This "before mailing" part is new and opens the door for a much higher level of surveillance.