FWIW, at Kroger and probably other places, just ask for a card and tell them you're in a hurry and will fill out the form at home. Of course, never do that. Been using mine for years. I see it as a win win, they could probably get interesting correlations from my buying habits, but have no idea who I am.
Of course share phone numbers work too, as another poster mentioned.
Of course share phone numbers work too, as another poster mentioned.