How come when y'all talk about competition, ya never talk about stockhouse.com? They seem to have a fairly decent setup including a sort of Private Messaging for free. They seem to be oriented towards Canukleheads & Aussies and could be a nice complement to your mainly US base of members.
Your greatest competitor is likely to be the rapidly evolving 'technology of dialogue' as the weblog phenomenon continues. Your own efforts to bring imbedded multimedia here are noteworthy and appreciated, but I believe that if you could add RSS syndication it would truly be a breakthrough that would increase your traffic significantly.