Brick-and-mortar retail stores including Macy’s Inc., Best Buy Co., J.C. Penney Co. and Staples Inc. are using Twitter, Facebook and YouTube to generate online buzz, luring shoppers to their stores and Web sites with special sales and promotions. More than half of retailers are including social networks in their marketing strategies today, up from 4 percent in 2007, according to a survey by BDO Seidman.