Truth be told, I've never heard of reverse graffiti before. And I like it! Not just the anti-vandalism approach, but I also like the silhouette-appearance of the style.
I'm fine with regular graffiti too, as long as it's appealing to the eye.
There's a big wall near my old school that had a lot of crude faces and, uhh, private parts - drawn on it until a professional artists went and sprayed this sick image onto it.
Now the wall is used for advertisement graffiti, and it looks pretty!