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.
BanksyPeople are fond of using military terms to describe what they do. We call it bombing when we go out painting, when of course it's more like entertaining the troops in a neutral zone, during peacetime in a country without an army.
Banksy