Spotted in Boston: Street Art?

I enjoy reading a few blogs about street art so I'm always on the look out for good examples wherever I travel. In Boston the other week I spotted this billboard that I had to give a good long look at to figure out if it was just falling apart or if someone had done this intentionally. In the end I figured it was just something that happened, but I love the idea that the rough/dirty reality is being revealed behind the pristine image reminding you that you "can't buy happiness".