According to the first amendment’s freedom of commercial speech theory, comparative advertising should represent the ultimate in terms of “right to speak” and “right to listen” in the marketplace of goods. Although the first right is severely regulated by government and private bodies in order to insure a greater protection to consumers exercising the second; this goal is not always achieved. Thanks mainly to the FTC’s initiatives and the support of its private pupils, consumer protection has evolved from “caveat emptor” to “caveat vendor.” The practice of comparative advertising might also make its contribution to the expansion of advertising’s Latin vocabulary with the addition of a third expression, for competitors’ use only: “cave canem.”