Mr. Fuller's Wiki
I definitely like the idea, but the setup at WikiSpaces seems very basic. I'm sure it's fine for my purposes, and I probably shouldn't expect more for a free service.
Blogs and Wikis definitely have their own space and should be able to coexist without any problems. The main purpose of a blog is for one person to share information with a larger group (mainly, teacher to student). A wiki is designed to let a large group of people share information with each other (in this case, students).
I don't think there's any reason a teacher would HAVE to use one over the other, or both, or whatever. Each can be molded to fit the teacher's needs.