I too was thinking that a big laminated sign on their door or front porch that says "WE DO NOT HAVE YOUR PHONE", followed with a paper describing that their location is commonly given out when more accurate location is not available. Now that they've had some press, a pamphlet box (like realtors use) containing printouts of some articles would deter most people.

It might make some people more suspicious ('maybe this is how they cover it up'), but should send most people on your way. Your idea of having a police report on file and contacting the local police department is even better.