Can Graffiti Be Above The Law?

The UK law is serious on graffiti - it's an illegal act, written into the Criminal Damage Act 1971 - graffiti sprayers can get fined as much as £5000.  It's not just a dislike of the media spotlight as to why Banksy does his work covertly.

And yet....and yet...look at how local counciles treat Banksy's own graffiti. It often remains on the walls. I can only think the local council alert the property owner first with an indication that their property may perhaps have just doubled in value :).

You see, Banksy's work automatically raises the price of a property that happens to have had one of its walls sprayed by the great artist.  And so councils have been known to leave the wall intact with the graffiti there rather than have it cleaned up.

Is this a case for graffiti becoming acceptable in certain situations? If the public don't complain, and the owner of the property that's "vandalised" is delighted that he's just made an extra £20,000, can there be a victim?