hey jeff,
the idea sounds appealing and interesting but the problem you didnt realize is that there are many webmaster forums out there struggling just because of the attitude of their members! it has been seen that the members in a webdesign and seo forum would not spill the secrets and things they know and things which they have learnt in so many years and they might just be interested in posting articles in a paid-to-post forum by copying and rewriting articles and does no good.
i think i had told you this before when the domain webmaster.in was selling on sedo and some body just posted that thread here at inforum.
the thing in domaining is that lets say by example that you say that your domain value is more because you own a 'geo' or 'generic' domain and so once the word is spread other people just google for its terms and understand what a geo or a generic domain means even if you dont wanna share it, but in web design and webmasters thing is different, lets say a guy said that his site's alexa rank is 55k and pagerank is 6 and so he is selling it for $8k - high value but you cannot google and find out how to get alexa rank of 55k or pr6 easily and people dont like sharing such info and there is no way you can know how to make that alexa rank of 55k unless the maker of the site or some other person who already knows it will tell you.
this is some of the reasons why i think a webmaster's forum isnt sucessfull online though there are many out there and at some point or the other the admin of such a forum realizes that it cannot continue for long so he either sells or stops it. just 2 exception of sp or dp is that they themselves publish ebooks and articles etc to help their members, but you wont find a member telling the guide to get a pr6 anywhere online for free of cost and even the paid article would be a re-written one of some other copied article.
though we can surely have a forum for non-technical topics of webdesign and seo where people can copy paste articles from other sites to there and a marketplace of web designers, service providers for such services and that would be good i think so! if you can manage to make a DP alternative webmaster's forum, it wouldbe the new years gift for people who are tired of geting banned there without any reason. as you see, here lies the market, more than half the forum population is banned at DP an they make fake accounts again and get banned again because they arent getting a better marketplace to trade at, so making a DP alternative would be the best i can advice. Atleast those DP mods can no more be proud of their stupid power to ban on the click of a mouse and the DP admin who doesnt even care to reply to banned members will have to beg to get new members on their old and totally spammed forum where they dont even have a good looking Vbulletin skin installed.
let me know what you think! a DP alternative is what i would highly recommend. atleast DP must have some end someday xD isnt it high time for them to format their server's hard disk and say... bye bye! xD