Facebook highlighted on Wednesday two ad campaigns in an attempt to persuade advertisers that its massive membership base and ability to home in on specific audiences makes it a more effective advertising platform than broadcast TV. The No. 1 social network revealed in a blog post some details about marketing campaigns from AARP and the American Legacy Foundation to show how Facebook can target specific age groups among its audience of more than 1 billion global users, which rivals the number of people watching TV. Facebook is hoping to tap some of the billions of dollars that advertisers dedicate to television commercials to reach large groups of people. For an advertiser, in Facebooks view their users are more engaged than when they are watching TV, said Debra Aho Williamson, principal analyst at research firm eMarketer.