I've been swiping my card at various chains for years, but I never saw any evidence of anything really malevolent in the practice. The threat was purely hypothetical.
Then today, my wife went through the self check-out and it printed out what appears to be a custom-generated advertisement for "New Morningstar Farms (R) Asian Veggie Patties! Introducing a sweet and spicy twist on traditional veggie burgers." This being North Carolina (pork-land, where "Asian-style vegetables and hints of chilis, garlic and ginger" aren't going to get a lot of folks' mouths watering) it's almost impossible to believe this isn't the first phase of some sort of creepy direct marketing campaign.
Still, it seems futile to dump the little keychain card, as this will only result in me being asked if I want to sign up for one every time I want to buy groceries.
-WD