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 FTC Cracks Down on Blogger Payola, Celebrity Tweets Rules on Endorsements and Testimonials Extended to Social Media By Michael Learmonth, Published on October 05, 2009 35 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.