I haven't written on the walls at ucb or places I respect - but - I do carry around a permanent marker because I am one of the people that draws dicks on subway advertisements and sometimes writes other stuff.
But my specialty is mostly dicks. Usually they are going into people's eyes or mouths or stuff like that. There's so many great possibilities!
It's fun and a good way to pass the time waiting for your train.
I also sometimes, when I'm really drunk, will write on the walls of bar bathrooms, usually if it's got writing there already.
Oh and also on the last night of Mo Pitkins since it was closing, I drew a lot of dicks on their wall on the various comedians.