I don't think this is a good idea.
why? for the simple reason that anyone can say something in it. You don't need to register to post a comment in the forum, so in that sense, a shoutbox already becomes useless. and a lot of users don't bookmark japanforum.com, but start from japanforum.com/forum. so they won't even see the box.
good suggestion, but i don't think it would work out in this situation.
