AGAIN, no one said graffiti is talent. We are talking about artistic talent that could be put to use in other forms of art. To be good at grafiti (good as in the thing to actually represent a picture not just a pointless scrawl) you need to have an eye for art. That is a talent. Not one person has said graffiti looks nice.
In lanzarote someone once used spraypaints to draw me a fantastic picture of an orca jumping a waterfall under a huge moon and shooting stars. Whats to say that isnt using an art talent he Once Upon a Time expressed as pointless grafiti, but now does this. Does he not have talent because he once did grafiti?