From Charlie Kratzer in Kentucky who decorated his whole basement in Sharpie line art to Meilena Hauslendale (she managed to nab the SharpieArtist.com domain name) who sells her Sharpie and Watercolor Artwork to a wide swath of the population. Even more graffiti inspired artists like Chris Dunlap (which seems a more classical fit to the Sharpie marker) has done some cool stuff, and even tricked out his Pontiac Fiero then covered the right side in Sharpie. In my own personal endeavors I've used Sharpies as a compliment to just about anything I've ever done. Painting a black line that is smooth and even is just to difficult for me to do with a brush.
Of course the people who work at Sharpie wouldn't be in Marketing if they were unable to recognize this burgeoning audience of artists and market to them. So Sharpie created Sharpie Uncapped to showcase some unique uses of their products. This is one of those gray areas of marketing that nobody really understands. If people are using your product to create underground art because your product is common place, and you take that underground art and promote it on your fully branded glossy web 2.0-ish site, does it degrade the very underground nature?