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 Brands on Facebook: Advertising Is Optional Marketers From GNC to P&G Weigh in on Social-Platform Strategy By Ad Age Staff, Published on May 17, 2012 7 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.