To me, there is a difference between street art and graffiti. Graffiti, in my mind, is "tags" like names, nicknames, or gang symbols. We had a lot of graffiti in my neighborhood in Jersey City, and I didn't like it.
Street art makes an area more beautiful, brightens your day, and brings color to a drab cityscape. Now, obviously there's the question of whether the building owner wants the addition to their building, and that's what makes in controversial.
On our honeymoon in Paris I saw a lot of great street art.
One of the more famous examples of street art is the "space invaders" by Invader which can be spotted all over Paris, if you have a keen eye.
Some of the most clever art I enjoyed was made with stickers on existing street signs.
In the shadow of the Eiffel Tower, even the crosswalk man carries a baguette.
This last one was in the red light district, obviously!
And some more traditional street art:
Coming soon... a few great street art photos I snapped in Iceland!