Here are a few examples of reverse graffiti (the links also contain some interesting narrative):
(From Durban, South Africa, located at: http://inhabitat.com/reverse-graffiti-south-africa n-artists-tag-walls-by-scrubbing-them-clean/ )
(Alexandre Orion – Skulls in São Paulo, located at: http://www.environmentalgraffiti.com/featured/35-greatest-works-of-reverse-graffiti/1949?image=20 ; the other images in this slide show are also noteworthy.)
(Singapore: located at: http://1outdooradvertising.blogspot.com/2009/01/reverse-graffiti-by-caltex.html;
what is surprising is that this is a legal advertisement.)
More to Be Added!