In the US, most large grocery store offer a card that you can use which gives you various rewards, and in turn allows them to perform analytics on their customer base.
Historically, these rewards were related to coupons for products in the store. However, this means that there is no benefit to using your particular card instead of someone else's.
More recently, the grocery stores have added other bonuses. The one that I'm most familiar with is for fuel / petrol. They team up with some fuel brand, say exxon, and when you've purchased enough on your loyalty card, you get something like $0.05 of your per gallon fuel costs.
The scheme with the poster above breaks down, because you need the physical loyalty card to use the fuel discount, and it's unlikely that everyone is refueling their car an equal amount each week, and that everyone is purchasing an equivalent amount of product at the store each week.
