I’m sorry, I might be misunderstanding how loyalty cards work... do they detect each other and report back to home with what other cards they have been in proximity to?
They're a scenario where people have willingly given away privacy to corporations in exchange for pretty minor benefits (largely, discounts that just bring the prices back to where they'd have originally been).
The cards themselves detect each other without me knowing it?
Checking into to JimmyJohns with a loyalty card is not the same as the guy I passed on the street's phone checking my phone and both letting JimmyJohns HQ that we passed each other at 12:53 on at 643 West Main St.
Hell, vast numbers of people have been doing it voluntarily already with loyalty cards.