In the beginning bands and artists would advertise their work with grafitti and posters placed illegally on the walls and bus stops in highly trafficked places. Now more civilized advertisers commission grafitti for rented walls and place posters on temporary walls at construction sites. But Snapple was frustrated by a lack of rentable wall space to promote their recent Summer Free For All promotion in Boston. So their agency, Street Attack, put the posters and grafitti on large boards and hung them on fences, etc. Considering how well this worked, we can expect to see more "temporary billboards."

Media Life Magazine: On the move: Snapple goes awilding, 2006-Jul-7, by Samantha Melamed

Luke Garro, Street Attack’s director of network development, says the movable spaces enabled Snapple to achieve the young, edgy, grassroots feel it was seeking. But it also made it possible to transport the media, like the mural, to all of the campaign events.
“We thought, how can we bring this to the areas they want to get to?” Garro recalls thinking. One side benefit, he says, is that the posters boards seemed to have a longer life than the average posting. “In places where I thought they would be taken down pretty fast, they were up weeks later.”