> Imagine if border guards seize money willy-nilly.

This jogged my memory, though I couldn't find the example I was thinking of. But here's an item that is pretty similar:

https://en.wikipedia.org/wiki/Tenaha,_Texas_asset_forfeiture...

Edit: Not on the border, btw. Just people travelling inside US. I guess it was their mistake to carry cash instead of getting a bank check or something.