Hmmm... interesting.
I can see some real value in using Facebook pages as a news feed. The polling app was another interesting feature that wikis seemed less able to accomodate.
I can also imagine placing links on Facebook to a PBWorks wiki to lead students to assignments and other course documents.
I found a lot more flexibility on the PBWorks wiki, though Facebook was a better media conduit. PBWorks could handle file exchange, not merely posting. It also allowed editing in addition to comment threads, and both have their place. The wiki could almost take on the look and feel of a website, with adaptation and evolution, where Facebook maintains a more static interface.
Truly I suspect I would use both, and other online resources as well.
