I use to have an anti-loyalty card.
One grocery store had a courtesy card they would scan for you if you forgot yours or just asked for it. Well the card number shows on your receipt... Add an online barcode generator & you have one anonymous anti-loyalty card.
I loved using it. Got a funny look & question once or twice since it came up on screen as courtesy card.
So any chance the serial / MAC won't be correlated with individual purchases?