Alan Buchanan surveys the answers in the literature to the question of what rights add to duties in: Buchanan, Allen. “What’s So Special About Rights?” Social Philosophy and Policy 2, no. 1 (1984): 61-83.
Buchanan has an interesting take on Nowheresville: it’s way of waiving duties would be incredibly inefficient.
There is also some interesting discussion about the usefulness of rights for settling questions of compensation in this article: Morris, Herbert. “The Status of Rights.” Ethics 92, no. 1, Special Issue on Rights (1981): 40-51. [JSTOR]