A local gallery, concerned about the amount of unsolicited graffiti defacing local buildings, begins a spray can buyback program. Anyone with a full can of spray paint can sell it to the gallery at face value, no questions asked. Used spray paint cans are pro-rated, priced by weight.
In response, taggers start stealing their rivals’ paint. Adding insult to injury, they tag the paint cans before selling them to the gallery.
To encourage further participation in the program, the gallery puts the tagged cans on display. The cans are secured on shelves behind wire cages to prevent theft.