Here is an excerpt from one Melbourne student's blog that seems to indicate that blogging can challenge students to new ways of learning.
As part of my journalism course I did Hypertext Theory and Practice, which was the basis for om_blog. This subject was a turning point for me because it introduced the learning theories behind blogging - that the ongoing nature of a blog relates to the process, rather than the outcome or product. We had to maintain a blog community in our class and create a hypertext in Storyspace. I know that most of us found it a challenge because the learning methods were radical to what we had been use to. But the real appeal for me was the idea that we could use an exploratory model rather than a conclusive one. For example, the assessment was our blogs and a hypertext rather than the regulatory 'intro-body-conclusion', word-limited essay that restricted the amount of problems we could discuss.
Although it worked for this student a quick look through some of the other blogs on the site would indicate that the take up wasn't great and a number of the students seemed to be just going through the motions.
Adrian Miles the teacher for this course keeps a regular blog and reflects here about assessing student blogs
The idea of establishing an "assessment matrix" is a good one.
An assessment matrix is provided that indicates the sorts of qualities an entry ought to have for each grade level (a high distinction entry would have qualities that ...) and a self assessment exercise is held where all students are able to evaluate a nominated entry against this matrix. This lets students concretise the grades in relation to their own work and demystifies what good, poor, and excellent work is