The post that was quoted here has been removedWhile I understand the difficulties that councils are faced in determining what has artistic merit and what does not, thus making a zero-tolerance attitude easier, I think the best way to work it is to make certain spaces public walls. and have the zero-tolerance apply to anything that is not among these. That way, if you really do consider yourself a graffiti artist, you have the space to work with, but you have no excuse if you step outside of that.
Also, for anything that's not a designated graffiti wall, but the artist believes taht they think that a particular space would work well for a particular piece they have in mind they can apply to their council. That may not be in the spirit of graffiti art, but by mainstreaming it in such a way I think the costs tot he graffiti culture would be outweighed by the benefits for their art. Alternatively, if the adrenalin rush of defacing non-designated zones is what the artist is after, then let them take the risk of getting their few months in jail. Just because someone is an artist doesn't mean they can get away with vandalism by calling it art, whether it has artistic merit or not.