I just read Fred Wilson's post From Blog To Forum, and it struck a cord with me, relative to a closed discussion forum in which I participate with a group of trusted associates. While the subject area of Fred's blog is different from the discussions of that private group, the behavioral patterns are very relevant to what that group is trying to create, which is a powerful forum for exchanging ideas and challenging one another.  Two key differences, though, are (1) Fred uses a blog whereas this private group uses a discussion forum and (2) Fred's blog is entirely open to all, this group is not.

This led me to ask the private group to consider those two points as we talk about the future of our group. Then, I realized that my reflection on these points would be good perspective to share with anyone who's interested. So, in the paragraphs below, I call out what I believe the the most important differences between a blog (which is typically open) and a forum (which can be either, but I'm especially focused on those that are closed, like the one I mentioned above).