Strangely attractive (read: very hot) comedian Demetri Martin has a great section about graffiti in his routine. He quite rightly points out that most wall scrawls make passionate claims about political affiliation and truths about life.
However, Martin encourages everyone to embrace the idea of indifferent graffiti. For example: "I like Sheryl as a friend, but I’m not sure about taking things further," and "Toy Story 2 was okay!" Martin's comedy routine has inspired a new wave of actual indifferent graffiti.