E-cast Billboards
Interactive e-cast billboards have been scattered around cities, which allow people to experience the rush of creating their own graffiti. Choose some colors, write a message and Sharpie makes it possible for anyone to leave his permanent mark on the side of the bus stop or the public phone or anywhere else billboard adverting may be experienced.
http://www.thecoolhunter.net/ads/Interactive-Sharpie-e-cast-Billboard/