I suspect that the suggestion that the bank just didn't want to give change to someone without an account and was just making excuses is the most likely explanation in the case of the $100 bill. Bankers, in my experience, often tell untruths out of ignorance; but occasionally I've seen it done as a matter of convenience.

In the case of the story linked by Bdub, it is possible that the spies have asked banks to report "unusual large transactions," but I haven't heard of any such change.

It has been a regulatory requirement for several years that any bank processing a cash transaction of $10,000 or more must report it. This is part of an anti-money-laundering packet of laws passed some time ago, at the time purportedly as part of the "war on drugs." The last time I checked, the amount that triggered a report was a specific included part of the banking regulations, so "bending the rules" to apply that particular law to lesser amounts would be ... bending the rules.

This is probably a case where the law said "do it" and the Banking and Commerce guys wrote the rules, so changing them would probably be fairly easy; but some public notice would be expected in normal times. Full compliance with the reporting requirements would require the bank to "certify" the identity of the person making the transaction, which in most cases would mean submitting copies of notarized copies of identification documents.

The old statute/regulation cropped up (or at least made the news) most often when someone attempted to pay cash for a new car, or even a recent model used one. Auto dealers dislike intensely having to do the extra paperwork to get the cash deposited. (That's on top of their dislike for not getting their bit of financing fees and interest, but that's another topic.)

John