This was a brilliant effort by the Candian agency rethink for the Contemporary Art Gallery in Vancouver, BC.
To quote their web site: "50,000 buttons were displayed, each printed with a single word representing one of a hundred possible responses to contemporary art. The public was free to walk away with as many buttons as they wanted in this interactive promotional installation for the Contemporary Art Gallery in Vancouver.
The text on the wall reads: THIS IS CONTEMPORARY ART."
This is great stuff. If this image isn't big enough, go to the site and search the Contemporary Art Gallery under "Archive".