Those ‘green’ reusable grocery bags aren’t just saving the earth ya’ know… those reusable bags are awesome little marketing tools. When a person sees another person carrying one, the logo is noticed and the store is noticed too. According to Jonah Berger, professor of marketing at the Wharton School of the Univ. of Penn and author of Contagious, Why Things Catch On, “The easier it is for people to see that others are doing something, the more likely they’ll be to do it themselves.”