Wait-- not that I necessarily disagree with your entire point, but I have moved several times in my life and every single U.S. library system I have been part of (Houston, Boston, etc) has required some form of confirmation that I live in their taxation/service region. Some of them are nicer--we'll mail you a postcard to confirm you get mail!--but the verification is there.

So I think there is some warrant to restricting access to those who have contributed.