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 Facebook's Ad Business Is Firing On All Cylinders, but Mum's the Word on Teens 53% of Ad Revenue Was From Mobile By Cotton Delo, Published on January 29, 2014 3 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.