I know they got in big trouble years ago, pre-internet. You stuck stamps of the magazines you wanted onto a card pre-printed with their name and address. Their return envelopes had a big cutout in the front for the address to show through, and on the back, star cutouts over the places for the stamps. They could see without even opening the envelope whether or not you had ordered anything. And if you didn't, they just tossed your entry. They got in trouble when the local landfill operator noticed the bales and bales of unopened PCH return envelopes and reported it to the Federal Trade Commission.