And in answer to Joe's question, what people would think about banning guests from initiating BS threads, I think that is reasonable. I don't go 'below the line' all that often, just when killing time; it seems to be a place for folks to hang out and chat about whatever they wish, which is all right, but is not necessarily appropriate for strangers to wander in. (We don't like strangers in our 'break room' at work either.) That might indeed help, but not cut visitors out from the primary networking and information sharing of the music related portions and the DT.
Come to think of it, why would a non-member choose to start a non-music thread on a music site, other than to stir something up? It seems to me more reasonable to go to a site on whatever non-music topic they wish to bring up.
I would hate to see guests banned altogether, both because of my first experience which I suspect is fairly typical, and because of work restrictions on cookies and the valuable visits of well-known musicians who drop in.