Brands have been hawking product on their Facebook fan pages for no more than two years now and yet the promise of F-commerce has the retail world buzzing. One prediction says social commerce will top $30 billion globally by 2015 with Facebook-generated sales one of the primary drivers. Certainly brands like Gap, Delta Air Lines and 1-800-Flowers.com have seen some returns on their early investments in setting up a shop window on the world’s busiest social network.