A recent favorable opinion by U.S. Supreme Court Justice Anthony Kennedy plus increased action in Congress have made it more likely than it has been in 50 years that out-of-state retailers will be forced to collect sales taxes in states where they don't have a physical presence. Half a century ago, of course, the volume generated by such sellers, who did their business via catalogs and snail mail, was tiny compared to the sales spawned by the rise of the internet.