I've recently been taking part in an online discussion about blogging for learning. (http://scope.lidc.sfu.ca/mod/forum/view.php?f=148 - I think you have to login to read/ take part)
Quite a significant part of the discussion was taken up with the discussion of differnet tools.
As I was singing Elgg's praises, I realised one potential issue for users when they have Elgg locally installed.
Most Universities etc., are likely to limit registration to internal users, though readers can be external.
If one sets comments to be logged in users only, then the world can see, but not comment on particular posts. It also means that a student couldn't set up, for example, a group for friends from home.
If there was an account type that just allowed commenting, possibly only obtainable through invitation from / request to the (student)blog owner, then, I'd have thought, the University will be statisfied that external users aren't using up lots of server space, but the blog owner can extend her readership & community to those outside the immediate University environment.
