The National Retail Federation estimates overall retail will grow 3.5 percent in 2008, the U.S. Census Bureau projects that ecommerce sales will increase 17 percent in the period, according to a new report from Retail Systems Research.Major retailers that generate $5 billion or more in annual revenue have an advantage, as they have more experience in multi-channel retailing. They are more likely than small and midsize retailers to view the online channel as an extension of their business instead of just an outlet for excess inventory.