The driving mission of the Wal-Mart corporation is to make money by saving its customers money. "At Wal-Mart," the company says, "everything we do flows from our purpose of saving people money so they can live better."

This week, Wal-Mart's truthfulness about "saving people money" was called into doubt again. The retailer's cost-saving claims in its advertising were labeled "unsupported" by the advertising industry's cop -- the National Advertising Division. The...