Remember being younger and writing all over stuff? Benches in the locker room at school, walls in stalls, etc. “Dave loves Michelle 6/8/10″, and drawings of random things. Remember the Million Dollar Homepage? A limited amount of space for sale at $1 per pixel, 1mm pixels.
Why isn’t there a big graffiti wall on the Internet. Simple tools of a paintbrush that can be fine size to thicker. Select color. You could draw anywhere on the “wall”.