Well... I am a huge idiot, so I guess it's ok for me 😃
Actually, it might be a good idea to have a separate forum for website critique. If a person's motivation for requesting critique of his site is solely to spam and get us to visit, That's really not so bad. I think s/he'd be motivated to write good code in fear of getting blasted by critiques. Of course, I think we'd have to limit it only to PHP-created sites, right? We'd need a good moderator to keep an eye on things and not allow blatant spamming.
However, limiting the ability to start new posts to those with a large number of posts would prevent newbies from posting their questions -- which of course sort of defeats the purpose of the board. I don't think that is a good idea -- unless you meant only for that particular forum.
Even so, some newbie might try his or her hand at putting together a site, and want some genuine feedback. If they were limited on posting to the critique forum, they might just post it to the General Questions forum or Echo Lounge, completely defeating the whole purpose of creating a Website Critique forum in the first place!
My vote is "yes," let's create the forum, but moderate it carefully. I'd be happy to be one of the moderators if you like -- I would suggest having two or three to keep an eye on things.