Definitely people who write checks. I specifically try to avoid going in lines with elderly women who always seem to be the ones to do this. If you want to use your checking account, just get an ATM card. Faster, safer, and easier.

As for the loyalty cards, I've gotten some applications where I can just check a box and not provide any information. In general, I do provide valid information though most of mine are now probably out of date. Not that I use them much anymore since I don't like any of the grocery stores around LA (either too expensive or not very good). I miss Wegman's from upstate NY (or actually most stores from northeast).