German artist Aram Bartholl often juxtaposes online life with real life, as seen in his giant Google Maps indicators and actualization of World of Warcraft avatars. One of his recent projects is to place CAPTCHAs -- the images of letters and numbers used to prevent computers from creating accounts with online services -- in public spaces. Bertholl places them next to graffiti tags because graffiti, like CAPTCHAs, are codes that can only be read by certain people. The project is called "Are You Human?"
via Make | Artist's Website