Open course blogs offer lots of interesting possibilities: convenient dialog among students, feeds (why haven't our CMSs incorporated these by now?), serendipitous participation by "outside" experts, simple interfaces, flexibility, etc.
At UW-Madison, I've seen a number of faculty use blogs as the centerpiece for their courses. Greg Downey's courses provide excellent examples of engaging students through course blogs.
However, blogs themselves will not overthrow the traditional CMS. There will always be the need to provide online exams, drop boxes, gradebooks, secure feedback, and all the complex integrations with various campus systems.
As the article above noted:
But despite a slew of jokes about Blackboard throughout the day, many attendees admitted that when the course-management system works, it offers easy-to-use features that students and professors have come to rely on. Even those speakers who encouraged professors to use blogs instead of Blackboard said that universities should probably support both.
Blogs have their place. The next generation of course/learning management systems will need to take cues from tools such as these in order to be relevant and provide useful user- (and especially learner-) centric environments.