I feel like there are a few things that need to be defined in this discussion because I feel like there's some sort of disambiguation of terms being used to describe what people want... (Building online communities is part of my job, so... I can't help but interject here.)
Any online forum can be broken down into two main categories of people. Authenticated users (logged in) and non-authenticated users (logged out). Both of these groups have permissions of things they can do.
Authenticated users are participants in the community. They can be broken down into subcategories like administators, mods, categories of privledge based on post count, etc.
Non-authenticated users are not participants in the community, they're observers of the community thus when a user is logged out, all they can do is read the posts on the forum.... Unless of course, you've set up the forum to not allow non-authenticated users to read.
General terms defined, this is what I think...
I don't think it's a good idea to restrict certain sections of the site based on post count. This creates rifts in the community, and can discourage people from becoming active members in the community if the bar is set too high... and in a community that's got an active member base that's as small as this one, you don't want to add additional barriers to participate or else the community will die.
However, I do think it's a good idea to restrict certain sections of the site based on whether a user is logged in or logged out. This is not an offensive line to draw because a logged in user is part of your community, a logged out one is an observer of your community and it's perfectly acceptable to have 'private' areas that only your members can see.
I personally would draw the line between "public" can be read by all forums and "private" can be read by only members forums based on whether the section is prone to having general information threads or personal information threads... In the case of what we currently have on this forum, I'd say I'd leave most of it public and make "Life Stories and Blogs" a members only forum because that forum is most likely to have more personal information than just opinions.
To profile what our current community looks like... We have two main groups of people. A core group of people who are active posters who are fairly experienced (so far as i can tell) with polyamory, and a constant stream of new members who are often new to polyamory, looking for emergency guidence but are not necessarily interested in (at least at first) joining a community... and then there are some people who don't fit into either category... less active users... some of which may be experienced with poly but aren't feeling a connection to the community enough to post all the time, and some of which are new to poly and want to be part of a community but aren't experienced enough to feel comfortable answering other new to poly questions.
That defined I think the big question that we're trying to address is "How do we make this space an inclusive community?"
From my experience with forums in general, I have found that often times what really transforms a forum about a certain subject into a blossoming community is to introduce parts of the forum that are just about life in general. Yes, the focus of this board is polyamory, however when you're dealing with a community who are in varying stages how involved they are into that lifestyle, it can cause divisions between people who are experienced and not experienced... and I think life in general.... things like cooking, cleaning, entertainment, parenting, family issues, health, etc. are things that we ALL can bond over because regardless of you're experience level with poly... those are all things we're going to have in common.
Does that make sense?