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 Online Advertisers: Do You Know Where Your Data Has Been? Data Providers Keep It Murky, but That's Bad For Publishers and for Marketers By Alan Pearlstein, Published on August 08, 2011 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.