Clever. The question is, did the owner do this, or is the box itself meant to be art as well. Oh who cares just check out this picture:
The text reads:
All are welcome to express themselves in the box below.
and
Painting within the above box is hereby expressly permitted and shall not be considered “graffiti” in accordance with article #23 of the San Francisco Municipal Code
Via Public Ad Campaign via Boing Boing