Control is exactly it: I can't speak to Blackboard, but in the version of Desire2Learn we use, students don't have a "page" that is theirs (the so-called page is a horrifying joke, not something anyone could or would ever use for any purpose at all - and no one ever does; the majority of students don't even bother to upload avatar photos even though that is now an option, because it is so meaningless and useless to even pretend your presence matters as an individual). One of the things I like best about using a Ning (which I use instead of Desire2Learn for student blogging and interaction) is that the students' profile pages are the anchors of the whole system, with a comment wall (very much like Facebook). Each person has their own place, students communicate with each other via the comment walls, and the system promotes that person-to-person communication - you leave a comment on someone's comment wall and there is a link right here to "comment back" - etc. Small design things that reveal very clearly just what is supposed to be going on. The Ning belongs to the students and it thrives as their space.
There is NOTHING learner-centric in that way about Desire2Learn.