Graffiti...

In my opinion, graffiti is a bold way to express different points of view. However there are things that can be considered art, I mean... something that people like to see and appreciate, while there are others that just show vandalism and let the place where they were done extremely dirty, what's horrible!!
I've ever seen 'graffitis' which the authors were interested in pointing out what their opinions were about a political statement, for exemple. But there are many others 'graffitis topics' as this one: