I admire certain aspects of it. It's like, if there is an abandoned building, I'd say go for it.
I don't like tags, tags are just random scribbles by people who think it's cool.
However, I've seen dedicated work that I would feel bad to see taken down. However it is still vandalism, and even though I am fine with it being put on old buildings, I know that it is only temporary until they decide to revitalize. So i say take a pic and enjoy it while it lasts.
I feel that graffiti is part of the life of a city. It's been around for centuries and it's like cave paintings. When we are gone, some of these will tell a story.
Here are the unwritten rules though.
No private property.
Nothing on new property.
I think the work of many artists are amazing, but I understand when it comes to small buisiness and personal property. Random taggers arent street artists. And I also think it's good to ask permission to do a mural, My neighborhood has a few murals, one was sadly taken down and painted over.
The other 2 are a mural of the city, and an Aztec Calender.
This one was taken down: