I used to do a lot of this sort of thing when I was drunk (and sober, actually), but I stopped after getting arrested in the process of writing "LEGALISE MURDER: WHY SHOULD GOVERNMENTS HAVE ALL THE FUN?" on the side of this abandoned building, whilst completely smashed and stoned. I only got an adult caution, but I figure its not really worth the risk of picking up a proper criminal record for a repeat offence, so I only do small, subtle things with pens now. Not particularly HARDCOAR ANARCEEST but what can you do? I rather want to finish art college, as opposed to getting kicked out of art college for doing graffiti.
I have a suspicion it's not a super-effective method of doing things anyway.