I got an unusual letter in the mail from Costco a couple weeks ago. It referenced a Costco purchase from a few weeks earlier--a box of canned peaches--and said that Costco had learned that the product "may not have been up to our usual standards."
(Reassuringly, the letter also emphasized that "this is not a food safety issue" and there was no need to return the product.)
They also included a $10 gift card, significantly more than the peaches originally cost.
I don't know what might have been wrong with these peaches: I hadn't complained and hadn't noticed anything unusual. For all I know, they might have just randomly send me ten bucks for no reason.
But as a way to cement my loyalty, this was extremely effective. All other hassles of shopping in a giant warehouse aside, Costco is now indelibly linked in my mind to "Stands behind their products" and "Treats customers fairly."
I never knew I could be bought so cheap.