Wikis!

Last week, I was doing a lot of talking about using blogs in my classroom.  Being the bandwagon, jumper that I am, I'm really liking the idea of using wikis instead.  Having looked at this wiki for My Side of the Mountain, I was really impressed with all the information they included- most of it student-created.  What I really like about the wiki format is that all of the information stays put on one nice, neat site.  If I had each of my students create blogs, then tried to get them to read each other's blogs on a regular basis, that would be a lot of clicking around, especially for students who don't organize their bookmarks well.  (I assume RSS would be another solution to this problem, so I'll be back on blogs before too long.)  But I like the idea that students can easily go back and study at the end of the unit, stay involved with the class if they have an extended absence, and have the chance to work at a different pace if need be.

The thing I'm wondering about is assessment.  The example I linked to assigned different parts of the wiki to different students, so that would be easy enough.  The part that gives me pause is, does that really encourage collaboration?  Say Jack and Joe are assigned chapter 1.  They are supposed to write a summary, and their classmates add or change details to improve accuracy.  But will they?  If there is a way to see who has written what, that problem is gone.  I can tell that Susie added a few details that they missed, so she did a good job.  I can tell that Greg didn't write anything, and he was a bald-faced liar when he said he did.  But if I can't tell who wrote what, assessment becomes difficult.  I have concerns that many students wouldn't write anything in the Chapter 1 page, because that's Jack and Joe's page.  That said, leaving it a free-for-all where every student is expected to contribute something, but are free to contribute in whatever section they want, is a great way to hear some digital crickets.

So has anyone used wikis much in their classroom?  Do you have any ideas for assessing student writing?  Are my concerns about students contributing to the wiki valid?

Hopefully I can get this straightened out, because I'd really like to incorporate wikis this year.