Completely agree. Invite only and some sort'uv qualification based upon the ET member posting history in ET's regular forum threads.
The chat room can definitely be monerterized--- I can see having free form but moderated daily market chat then several times a week have a sponsor or expert in a particular trading style field questions and comments. I'll be happy to work with you in managing this aspect of the site. It will add life to the site and ramp up the bottom line, the instant feedback must be worth serious coin. Not to mention having a seperate marketing environment.