This has been done for a while, but I'm just getting around to posting it. Sorry.
In the interest of authentic assessment, I decided to give the wiki a test during a class. My students had just finished reading Fallen Angels by Walter Dean Myers and had to have an in-class seminar over this outside reading. Normally, students have to discuss an assigned book in a large-group environment. I thought this lent itself well to both a forum, which I've used before, and possibly a Wiki.
Students used Moodle to add forum posts with questions they had about topics in the story, and that portion of the day went quite smoothly. After that was completed, I had them work on a Wiki that described the various characters in the story so that all would have access to the most accurate information (telling a couple to be watch-dogs for inaccuracies).
The fact that the Wiki in moodle would only allow one student to edit at a time led me to revise the plan and create a google-doc that my afternoon classes could work with. The Google-doc allowed them to edit at the same time, but wasn't real-time. I am hesitant to use Etherpad due to the chat feature, though that was an option as well.
The overall product was not great with the Wikis while the Google Docs were a little better.