People for the Ethical Treatment of Animals (who have now formed a new branch, People for the Ethical Treatment of Shopping Carts) has been among the most vociferous critics of the practice of keeping shopping carts for human purposes. Most controversially, they have compared the practice to that of human slavery, juxtaposing images of shopping carts huddled together in their parking lot racks with images of slaves chained together in the holds of a slave ship. Unsurprisingly this tactic has been remarkable effective, eliciting great sympathy for the shopping carts and creating solidarity with the black community.