I find it helpful for students to discuss assignments among themselves. However, what I want them to discuss are the ideas and concepts, not just pass around answers.
I would like to be able to provide a discussion for each assignment. However, I want to moderate the discussion, i.e., the students can post to the discussion, but the post will not be seen until I approve it. That way I can suppress or edit posts that are just giving answers. I would also be able to provide supplemental information myself at that time.