I have a forum with about 58 posts, started the site 3 months ago,but didn't really have time to develop it...but when I checked it today, it has a pagerank of 4, the same thing happened to my another website....I must have a super duper 1337 SEO skill then..LOL..Joking...Any explanation?
I have also seen similar results for my site. I don't find time for developing my site, just uploaded home page and configured forums. I got PR5 for both. Now, I am looking for tons pages content for my site and tons of post in my forums.