Today, a company's slogan has become a launchpad for an entire advertising strategy. "Before it was just a line," says Marie-Claude Mayer, senior vice president at ad agency Publicis Worldwide. "Now it's an invitation to share in a brand's life." French car maker Renault SA, for instance, uses its "Drive the Change" slogan to encourage people to carpool, in addition to bolstering its image as an electric-car pioneer.