>And can anyone think of a true historical antecedent?

Actually, one just sprung to mind when i was reading this. When I was in school (many years ago) we used old fashioned wooden desks. It was common practice to write grafitti etc on them, but since it was often the same people sitting at any particular desk (we would only be in one classroom/desk for 1hr or so at a time) you would often get things like conversations, join authored poems, strange doodles etc. You could literally spend hours tracing the pouring over the desks in a classroom finding intersting 'posts' as it were..