If you've ever browsed the shelves at your local bookstore only to go home and purchase online, you're a brick-and-mortar retailer's worst nightmare. As former giants like Borders moved toward bankruptcy in 2010, U.S. e-retailers hit $165.4 billion in sales — twice as much as five years ago. Traditional outlets are left with one competitive advantage: customer experience, the talk of this Minneapolis forum. Barnes & Noble, for example, offers deals to those who visit stores with e-readers. "Best-in-class retailers," says event producer James Bickers, "compete on more than price."