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 Why Twitter Is Keeping Its Cards Close in 'Confidential' IPO Methodically Laying the Groundwork With TV Ties and Mobile Ads By Michael Learmonth, Published on September 12, 2013 0 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. Become a Member Already a member? Log in.