urban decay

I personally view graffiti as an art form. Some graffiti artists are incredibly talented and can breathe life into an otherwise dull expanse of gray. But where do you draw the line? While I think some of the work produced is abslolutely amazing, tagged windows and statues really arn't acceptible. Does such an opinion hamper the freedom of expression that is so prevalent with grafitti art or is it reasonable to expect a certain amount of respect?