Ziggy Stardust said:
Exit Through the Gift Shop
I love this documentary/mockumentary/performance art piece. It's rather brilliant in its meta-ness.
As for the difference between street art and graffiti, the boundaries are blurry. Graffiti is typically intended in some way to deface, whether as a political or social statement or just as good old fashioned anarchy. Street art can be graffiti, and the best, like banksy's work is definitely street art AND graffiti, but when it's a commissioned mural, it's street art, but not graffiti.
Then there's tagging, which there is a lot of in Chicago. I do not consider that street art, except in a few rare cases where it's done by someone with serious skill and an intuition for form and composition. I would say only about 1% of tags can be considered genuine street art. Personally, my favorite street art is the small, inconspicuous kind that you might not even notice if you're not looking for it. Here's an example I found crossing the street in Chicago this summer. It's made with the same material used to paint the white lines. (I had to take the picture fast or get struck by a car!)