I'll start one up!
$1000 per year annual dues and you'll receive:
- a nifty "Golden Seal of DN Profiteering" which you can emblazen on your site(s).
- a newsletter of some kind.
ok ... sorry, got carried away.
To be honest, marketing of names is an individual type process (everyone has their own way of doing it).
I think it would be very difficult to get people to agree on and adhere to some kind of common code of conduct.
Also, many DN resellers (successfull ones) have access to tools, registrars, processes, etc that others don't. Some kind of 'union' for lack of a better term would possible eliminate their competitive advantage in the marketplace and the acquisition of inventory (domain names).
But that is just my opinion