Street art or crime? I would imagine if it's your gable end or garden fence then you'll probably regard it as the latter, but if you are the one wielding the spray can then I guess you'd call it street art. Graffiti art has historically been viewed as a form of vandalism and a nuisance to society.
However, many academic institutes now regard graffiti as a legitimate source of academic study, and it is being studied as a reaction to injustice and disenfranchisement, a way to create awareness of socio-political issues, an expression of hope for the future, an effort to reclaim public spaces, an attempt to beautify or just a way to make people smile.
Like every other city, town or village, Edinburgh has its fair share of graffiti, a lot of it isn't art at all but random gang spray painting, but some is enigmatic and arouses curiosity.