This is really interesting. As an English teacher, my focus has been on using blogging as a way to motivate my students to write more, to write for real audiences, and to write more authentically than they usually do in school assignments. You can read my latest reflections on all of this here.
Your idea—teaching blogging as a set of communication skills, rather than using blogging as a means of teaching writing—is something I haven’t thought about at all.
Now I’m going to have to sit down and think about it.