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 A New Silicon Valley Rule? All Great Internet Cos. Build an Ad Network Even Publishers Who've Bemoaned Networks Have One By Tod Sacerdoti, Published on November 10, 2009 8 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.