Dr VAN raises an interesting issue because it speaks to the experimental nature of using blogs for coursework. Which is to say, even if as an instructor you regularly employ student blogs in your courses, your students will not generally be accustomed to it, so there's a certain amount of tweaking and adjustment that goes into adapting the form to an academic context. One of the biggest concerns in this range seems to be tone/style of engagement: it can be difficult to strike a balance between the horrible extremes of blog as informal chat/blather (the beloved house style of the internet) and blog as dead repository for student assignments.
My class actually started out the semester at the opposite end of the spectrum from Dr VAN's, posting only assignments and offering feeble peer-review style comments ("good use of quotation"). After some class discussion, we seem to have worked the comments in the direction of dialogic engagement with other writers' ideas; now and for the next few weeks I'll be in the process of getting them to loosen up a little bit and take ownership of their blogs, so that they can find their way into the course materials on their own. I framed the situation this way when I chose to lay first emphasis on individual posts as graded responses, which is the first tier of my blog grading policy -- I figured it would be easier to work backward from formal, alienated writing (i.e. homework) than forward from txtspk. Now I'm pushing the second tier of the blog grades, which is the overall grade for their blogs based on the rubric Priscilla posted a few weeks ago. You can find my notes on this point here. In other words, I've tried to "discipline" them first, then introduce the idea that they can take a more creative approach to their blogs outside of the formal assignments as an easy way to raise the "low stakes" portion of their grade. After the break, I'll be announcing a two-week contest for the most creative blog, to be determined by class vote.
I hope this two-tiered approach will produce a mix of dynamic blogs punctuated by occasional "formal" responses. I'll post later in the semester to let you know how it works out.
I do think it would make an enormous difference if I could have these students in a computer lab once a week, as I will when I teach the cluster next fall. (I've tried the laptop classroom, but the connections are so dodgy that the students get discouraged.) In the fall, I'm also planning to structure the blog assignments differently at the beginning of the semester: the first post will be a personal introduction (pass/fail), the second will be a formal (graded) response to a class reading, and the third will be an informal (ungraded) post on a topic related to the class. Thereafter, formal responses will be due about once per week. For the informal responses, I'm going to experiment with "lightning round" (10-15 minute) contests about once a week to see who can produce the most interesting/creative/funny post -- so there will be immediate incentives for informal as well as formal engagement with class blogs. I have a sense that this will keep them thinking about the discussion topics throughout the week, since it will be easier to win the contests if you already have something in mind. I've found that little games like this are also a good way to shift the pace of a class and keep the students engaged (plus they can be used as a reward/punishment system since they are usually well-liked). However, you really need a lab to do this kind of activity with blogs, because you need everyone in the same room during the contest to generate excitement.