Art or scrawl?

Some 'graffiti art' is decidly unexceptional, whether in colour, or monotone. But what appeals anout it to me is how quickly it changes. Whether that's faded, covered over by more 'art', or simply 'vandalised' by those who see it as vandalism, and an eyesore itself. Which goes back to the age old question: 'What is art?'. (Or in my case 'What is a photo?' )