StackyYou raise some interesting points and make great observations, but there are a few things I wanted to note.
First, some of the unregistered guests that you see are bots...some crawl through the website for Google, Yahoo, etc, while others try to make accounts to spam the forum with, something that used to plague us until we added better anti-bot measures to the registration. I'm not entirely sure that restricting the forums would result in more people registering though. We advertise our forums a lot in our recruitment message and our welcome message, and I think it's good that people can view the forum, see how our community and government functions, and then decide if it's for them. Personally, when I come to a forum that you can't view unless you register, unless I have a specific purpose for being there I usually won't bother with it.
I know of a few regions that have restricted their forums, but that's usually to try to prevent 'foreigners' from viewing controversies that may go on there and make the region look bad, not to pique guest interest.
Secondly, the post stats that we compile at the end of the month isn't for the purpose of emphasizing post counts over content, but to view trends and spot when someone might be losing interest in the forums or region. That listing only includes people that have contributed 1% of posts for a given month, which is usually between 10-20 posts, meaning that they've taken the time to come to the forums, register, apply for Citizenship or more rarely ambassadorship, and post a good amount of messages. If they drop off the face of the forum, it may be something to notice and ask why, especially if they're still maintaining a nation in the game...and I just compile the rankings because I think it's fun and kind of cool to see how things are trending, but I do stats for a living anyway.
We haven't utilized the stats for that purpose as much as we should, but now that we have a functioning Integration Ministry we should be able to actually investigate issues the stats bring up.
Just my opinion...I've included everything you've brought it in the chart, cause ultimately I'm looking for Citizen opinions, not my own.