This chart from ReadWriteWeb is telling, and it matches the story I heard while contracting at Best Buy, which was that Best Buy was flying high during the 2000s. They saw their main competitor as Circuit City, and the bestbuy.com website racked up billions of dollars in sales.
When Circuit City went under, Best Buy looked up and saw Amazon catching up fast. They have not been able to make the technological transition necessary to fight the online retailer.