Any source for that? Sounds almost too good to be true.
The loyalty cards can also backfire on supermarket chains. Safeway was sued for not notifying customers of product recalls even though it had the purchase data: http://www.progressivegrocer.com/top-stories/headlines/healt...
Ultimately, the shopper failed to prove his case. He claimed Vons was negligent for not cleaning up spilled yogurt, but during the trial somehow failed to prove (1) that there was some spilled substance which would have caused him to slip and (2) that his knee injury was caused by the slip and not by subsequent activities after he left the store.