Frank Boosman makes an excellent point about the need to find a way to set levels of privacy on one’s weblog (because it would be better to do that than to have to create several different weblogs each with mostly the same posts but different levels of security.
livejournal has this feature.
One might also extend this idea to “quality rings” where different levels of depth of your thinking were available to different readers, or eventually “payment rings” (like the Salon Premium model) where people could read your blog at one level for free or pay to be able to see the deeper level (or pay per post read at that level?)