You’ve read all of your free items this month. To register, get added benefits and unlimited access to articles, Become a Member. Already a Member? Sign in. Advertising Age Article Abstract Jack Dorsey's Square Wants to Eliminate Cash, but So Do Visa, Mastercard, AT&T and Google Nice Idea but Twitter's Co-founder Enters a Very Crowded Space Full of Players With Leverage Over Retailers By Kunur Patel, Published on May 24, 2011 8 Want more Access, Content & Connections? Upgrade to Membership. We are glad you are enjoying Advertising Age. To get uninterrupted access and additional benefits, become a member today. Register Now Already a member? Log in.