Although I have seen wikis before, this was the first one I participated in. I have actually done a similar activity with students but on a blog. I teach formal academic writing, so I gave the students a topic sentence in an original post to start with and asked students to write an appropriate sentence to build a paragraph--each student could only write one sentence at a time--we used comments to build the paragraph. The students had to obey the rules of formal paragraph organization. Again, the fact that my "class" changes every month (revolving door phenomenon), and that students are all working at their own pace, makes it more difficult to do a task that requires cooperation from a number of students.
Using a wiki to do this type of exercise is obviously easier. However, I found it difficult to do with the "creative" writing task we were given this week. That's definitely not my forte! However, give me something expository to write, and I don't know when to stop;-) Next time I want to do an activity similar to the one I did on the blog I mentioned, I will use a wiki instead.