A small furniture manufacturer based in Arizona recently received a nexus survey — a questionnaire about the company's business activity — from the state of Washington. With just two retail customers in the Evergreen State and a lone sales rep making an annual visit there, the Arizona company returned the form and thought that was the end of the matter. No such luck. Washington assessed the Arizona furniture anufacturer "a substantial income tax," according to Marvin Kirsner, a tax attorney with Greenberg Traurig who represents the company. "One salesperson was there for a total of three days over four years....