Some good photography on this thread and some interesting shots. However, whilst some of the "graffiti" might be witty / amusing and some of it is vaguely artistic, am I the only one that regards it as "criminal damage"?
Maybe I'm just an old fuddy-duddy but I would cheerfully prosecute any would-be "Wanksy" (or whatever his name is) and have them lick the wall clean if they did that on the side of my house.
It certainly is technically 'criminal damage', and for the tools who just want to paint the same old cliched tags for their own sake, then I'm a fellow fuddy-duddy. These are people who don't even have the creativity to rebel in a new and interesting way! They're not doing anything new, and they are even copying the tags poorly. I'd have no problem sentencing them to a lashing or two.
Sometimes, though, I really think that grafitti is fascinating and can really push the boundaries of what is considered 'art' and make us think of the role of public art. Sometimes there are artists who are not only skillful with the painting itself, but are also mindful of context and medium, and that can be thought-provoking.
Of course, if someone were to provoke thought it this way on the side of MY house, there would also be some lawsuit provoking happening on my end