The people who run our cities don’t understand graffiti because they think nothing has the right to exist unless it makes a profit. The people who truly deface our neighborhoods are the companies that scrawl giant slogans across buildings and buses trying to make us feel inadequate unless we buy their stuff. Any advertisement in public space that gives you no choice whether you see it or not is yours, it belongs to you, it’s yours to take, rearrange and re-use. Asking for permission is like asking to keep a rock someone just threw at your head.