Or all three?
I saw this on the sidewalk by San Antonio College facing San Pedro. What's interesting about this piece is that it doesn't involve adding anything to the public walkway (paint, chalk, what have you). In fact, it involves taking something away.
Yes, it seems that this was made with a stencil that was pressure-washed, cleaning the exposed areas of the sidewalk and leaving the rest dirty. It's semi-permanent, but the advertisers did not do anything that was technically "graffiti". They actually cleaned a little bit of the public space, but they did it in a way that promotes a specific event.
What do you think? Clever tactic, or just another way to get away with marking up public property?