For Mars, the biggest user of socially enabled ads, that strategy seems to be paying off in the form of big brand fan counts. Mars has nine of the 70 largest brand fan pages, according to DBM/Scan's Facebook fan tracker, with more than 45 million fans collectively. Kraft, which also invested heavily in socially enabled ads, has the third largest Facebook brand page, according to DBM/Scan, with more than 23 million fans for Oreo as of Oct. 4. But Coca-Cola Co., which has the biggest Facebook brand fan page with 34.5 million, was a relatively lighter user of socially enabled ad impressions, using only about a sixth as many as Mars. And Starbucks, the No. 2 fan brand page, used no socially enabled ads at all in July, and a well-below-norm 19% of its online ad impressions on social networks. Another reason to drive traffic to Facebook, is that brands are getting more exposure among friends of fans than the fans themselves. Messaging in socially enabled online ads tends heavily toward promotional or philanthropic activities, Mr. Zeman said, citing a recent Bud Light Port Paradise promotion and P&G ads focused on getting people to join its "Dawn Saves Wildlife" program for cleaning wildlife affected by oil spills. Get the full story at Advertising Age