Delete!
Aaron points to a remarkable public-art project in Vienna: Delete!. According to the MSNBC article, artists Christoph Steinbrener and Rainer Dempf got local government and all of the local businesses to agree to a two-week period in which all of the ads and signs for businesses in a particular shopping district are covered in bright yellow fabric and plastic. There are more photos on the project page, plus more info for those who read German. Also, a blogger provides more photos, including some of graffiti scribbled on the covered-up signs.