The US Government hates when you use cash, because its use makes it harder for them to spy on your private affairs and to tax or confiscate your private commerce. An implication of that I had not considered before is on gift cards. I was making a large order of Amazon gift cards for a Christmas bonus for employees when I got this email from Amazon:
We're contacting you regarding your recent Amazon.com order xxxxxxxxx, which included one or more gift cards. To comply with the U.S. federal regulations, purchases of gift cards from Amazon.com and its affiliated websites are limited to up to $10,000 for any customer in a single day. Because this order contained gift card purchases in excess of this limit, it has been cancelled and you won't be charged for any items in this order.