Graphic designer Stefan Sagmeister, in collaboration with lettering guru Jessica Hische and 150 volunteers, created this public installation in Amsterdam composed of 250,000 eurocents proclaiming, "Obsessions make my life worse and my work better." After it was finished, the installation was left unprotected to see how the public would interact with it.
About 20 afters after it was complete, when the plaza was empty, a man came through and started picking up the coins and putting them in bags. A neighbor, concerned that someone was "stealing the artwork," called the police, who tried to find the artist, and when they couldn't, they called a city cleaning company to bag up all the money and put it in a safe until they could reach the artist. Ha!
More on Sagmeister's site here, including a timelapse video of the installation.
Jessica Hische website here (tons of awesome typography/graphic design stuff to explore).