Allen Varney, who recently administered an exemplary game of Lexicon, presents a new spin on that concept, called Noteworthy. It has a GM and seems intended for LiveJournal communities (but adaptable to other forms of the weblog medium). Most LiveJournal RPGs I know of do fine without rules of any kind, but maybe with Noteworthy (or some revision thereof that gets made due to the original's Creative Commons license), that world will meet ours in the middle.