Retailers are hoping to expand their Twitter following during the busy holiday shopping season.  Twitter's Director of Retail JJ Hirschle [[ her-shal ]] says retailers of all sizes are offering exclusive bargains to their followers.  The country's largest retailers are looking toward social media to grow sales and make up for a disappointing Black Friday weekend.  The National Retail Federation this week reported sales were down eleven-percent during the weekend following Thanksgiving.  Customer traffic was also down, with six-million fewer shoppers stepping foot inside brick and mortar stores.