At issue is the "affiliate program" used by many e-retailers. Web site operators can provide a link to an e-retailer in return for a commission on any sale resulting from customers using the link. While the affiliate program may consist of little more than a non-descript advertisement on the computer screen, the tax consequences may be huge: New York state says it is the equivalent of having an instate salesperson. "It’s just treating the affiliate the same way we would treat any other type of sales representative," Mr. Spitzer’s budget director, Paul Francis, said in an interview. Under this novel theory, any e-retailer who pays a New York-based Web site operator a commission would be required to start collecting sales taxes on any purchase from New York, regardless of whether it originated from an "affiliate." "It’s a clever move," a professor of Internet governance at Oxford University, Jonathan Zittrain, wrote by e-mail yesterday. It wouldn’t take much more than a fringe novelist from Brooklyn plugging his latest book on his Web site- and providing a link to Amazon.com in exchange for a commission of the sales- to force the online bookseller to collect a sales tax from every New Yorker who makes a purchase.