Never. "Mere listings" of data (like the phone book) are not copyrightable. But also anything you write which is copyrightable is copyright immediately. You ca

Never. "Mere listings" of data (like the phone book) are not copyrightable. But also anything you write which is copyrightable is copyright immediately. You can register the work w/ the copyright office for some extra perks but it's not strictly necessary.