Frankly I always thought that such things were never allowed in Switzerland up until I saw some very spectacular graffiti spreading meters long nearby our block of flats. There is an underbridge passage for bikes and pedestrians with concrete walls of good 500 meters in length which attracts the kids with boomboxes and cartoons of spray paints. They hang around there regularly and respray the walls almost every two weeks with new "creative and evil looking stuff". These guys seem to be not even disturbed by presence of passersby constantly busy with their art assuming the bridge is their own gallery. I only feel sorry for the old man who must be a community public worker and he tries to wipe a paint out of all the visible signs on the bridge which also get covered in process.
What can I say? Perhaps hadn't it been for these kids to express themselves in similar form of art, we might have seen them occupied with much worse kind of stuff.