I headed up the team behind a similar project a few years ago called Classhive (www.classhive.com). The UI we built for the project is eerily similar to CourseKit, and we faced a lot of the same difficulties mentioned in this thread to get it to take off (which it ultimately did not). Even taking the one school at a time approach, it's still very difficult to get teachers to completely change which system they use when they know students are using Blackboard for every other class (even if it's an awful piece of software).

An approach that we didn't have time or the support to explore was building something that students would champion themselves, regardless of University or teacher support. This meant jumping into an area that might be controversial, and support things like the sharing/selling of notes, cheating, gossip, and more social interaction between students in large classes.

Until someone creates a product in this space that is inherently addictive and breaks a few rules, I do not think anyone is going to knock Blackboard down as the king.