It was a lot easier to put in someone else's phone number than someone else's prime account.

Back in the day we used to hold "store card swapping parties" where you'd bring your store card, drop it in the pile, and then everyone randomly picks a new one. Do it about once a month.

Now of course the store cards are tied to apps that give you coupons on things you buy, so it's more in your interest not to mess with them.