In the winter of 2001/2002 we contacted people in 35 countries around the world. These are the responds:

Australia Brazil Canada China Denmark Finland Germany Iceland India Iran Israel Italy New Zealand Sweden

Britain - a polite letter saying no thank you.
Hungary - a slip of paper saying "NO thank you", sent back with the pencil broken in two and the unused disposable camera and the empty notebook.
USA - “Return to sender. No such street number”