Excuse me kind sirs, reality control.
1). You are forgetting that ET is run as a business, and as such the greater the number of members/posters... well you get the idea.
If most members couldn't post they'd leave for greener pastures [read: fewer hits, less advertising revenue and site value].
2). What you are mentioning has already been done. NuclearPhynance sprung from some bad blood at Wilmott. The difference is that the guys who created NuclearPhynance are institutional traders (or belong in an institution - as one of its founders has comically stated in the past) and apparently have no need for the advertising dollar/Euro/pound - apart from the odd job listing which I'm sure generates enough to pay for the site's costs. Everyone knows the rules. Keep the signal to noise ratio high, any crap and people get blended. Certainly no "gurus" or system peddlers there, etc.