What I’d avoid is, things like loyalty cards — cash or not, discount or no discount. I’m sure if I sign up, giving my personal info, something tricky is written in fine print^* in the sing up form, in obscure legalese. There ain’t no such thing as a free lunch. If you get a discount, you’re actually selling your privacy cheaper than it actually is. _{*Some_instances_may_be_excluded._Your_mileage_may_vary.}