Traditional graffiti writers have a bunch of rules they like to stick to, and good luck to them, but I didn't become a graffiti artist so I could have somebody else tell me what to do. If you're the type who gets sentimental about people scribbling over your stuff, I suggest graffiti is probably not the right hobby for you.
BanksyGraffiti ultimately wins out over proper art because it becomes part of your city, it' s a tool; "I'll meet you in that pub, you know, the one opposite that wall with a picture of a monkey holding a chainsaw". I mean, how much more useful can a painting be than that?
Banksy