A novel, implementation (2006), was published as a series of stickers. It was written (and stuck around) by Nick Montfort and Scott Rettberg. This site tells you all about it. Now Montfort and Rettberg are planning a coffee-table photo book version. Really. Here are two of their instructions for this new version: "2) Choose interesting places to put the stickers up in public environments and stick them there. 3) Photograph the sticker, attempting to get photos of the sticker both at a close/legible view and from some distance, showing the placement of the sticker in its environment." Here are photos of a sticker stuck in Berkeley.