Some blogs are public, not much different in nature from an opinion column in a newspaper or magazine. Some blogs are truly private. (This one is obviously not, since you are reading it without special permission.)
A recent book, Here Comes Everybody, by Clay Shirky (2008), points out that, in a break from past patterns of communication, much of what is on "Web 2.0" -- blogs, pages on social networks, etc. -- is private communication (and some, I would add, is introspection) written for a target audience of one or a few, but published where all can see. There are imperfect precedents, for instance, a personal diary or a ship's log being published later, or an interview being broadcast to an audience. But for the most part, this phenomenon is new, and, being new, can be confusing.
So here is an explanation of this blog, and several others like it that are being created around this time:
It's an assignment (and will refer to other assignments) in a class,"23 Things," given by a library to its employees, exploring various aspects of Web 2.0. The target audience is other members of the class. However, because of the value held by librarians and teachers that information should be shared, anyone is welcome to read and learn. And in the spirit of the mixed-up mash of public and private that is one of the salient features of the new internet culture, it will also contain information that is of more general interest. (Warning: there may be, due to the topic, some navel-contemplation). It may even continue as a "real" blog after the class is over.