Where do you draw the line with street art?

I mean, which things do you consider art and which ones do you consider crimes? For me it's like this:

1) Drawings and paintings on walls: It doesn't matter if it's an abandoned place (or a wall in the middle of nowhere like at the end of this movie) or a house/building being used. Art is not about the medium. Of course that it would be better if they would ask permission to the residents of the houses and buildings. They might say "No" or they might say "Yes but I decide what you're going to paint", but that's art business.

2) Written graffittis: I used to think they were all crimes. But with this movie now I know that people don't just write things like "I was here" and "He loves her", and they don't just hide words from signs or alter them to say something dirty. Now I know they can write smart and poetic short sentences. If it's something that could work as a New Yorker caption, then it's fine by me.

3) Pasting signs: That's not something you would see in an art gallery nor in a book (unlike the previous 2 examples). And the people who put them there aren't necessarily the ones who made it. It's not a crime but it's not art.

4) Alterations: This is a crime because it's more permanent and because it NEEDS the aproval of others. You can always paint over buildings, but you can't fix a phone booth split in half. You can't ask an elephant if he wants to be painted over. And regardless of the original intention, forgering money will do more harm than the other things.

5) Breaking into others' galleries and putting your art there: Not just illegal; also pathetic.

For those who want to be street artists: Please remember that art is about expressing but expressing to others. If you don't respect your audience they will not want to see more of your art. Also, do it ONLY if you don't have another way. I mean, if you can't afford a gallery or you're constantly being censored for something that's politically incorrect but not immoral.