A blog entry should be a course activity. The reason we would want a blog instead of an on-line assignment is that one, the user has the option of making it public, and two, the user has the option to keep it completely private, including not letting the teacher read it. Three, there is the option to keep the blog entry beyond the timeframe of the course.
We have a course where the student is required to do reflection about themselves. Those reflections are important to keep beyond the course. Some students may view these as very private, and not want to share them publicly or even with the teacher. On the other hand, the teacher of the course wants the student to do those reflections. In other words, what is written is not what is important. The act of doing the writing is what is important.
Melissa