Shamelessly ripped from Wired.com’s Underwire blog:
Draw on public surfaces by removing the sooth and dirt. This guy did it in the San Paolo subway where the walls are covered with the usual subway dirt. The reaction of the government to prevent him doing it over and over: clean the tubes. Yup that’s right. This guy on his own managed to get the officials to consider cleaning up the tubes, and not only the one tunnel he was decorating, but all of them.