Well, I have to report a contrary view, in a way.

My wife and I had a Kroger card--that is, each of of had a copy of the card she had applied for. I misplaced mine, and when I was in the store I told the clerk that. "Oh, that's okay. I'll give you another one." And she gave me a Kroger card without taking any information at all. I don't know whether my wife's card accesses an account with our identity in some form or not, but mine doesn't. THEREFORE:

When we go to the grocery on Saturday mornings, I'm always in line in front of her, and I make a point of handing MY card to the clerk as I put the groceries on the belt. The purchase is unattributed.

Dave Oesterreich