A friend (tnx, Steve!) forwarded me an article from Searcher magazine, April 2003, by David Mattison. It's titled "Quickiwiki, Swiki, Twiki, Zwiki and the Plone Wars: Wiki as a PIM and Collaborative Content Tool"  and is a good overview, reference-rich and oriented toward librarians, of what Wikis are all about. It also includes a thoughtful interview with Bo Leuf (hi Bo!).
Along the way Mattison makes the insightful point:
While both wikis and blogs are extensible to the point that they become indistinguishable, the general design principles of wikis and blogs remain unchanged: wikis promote content over form, blogs promote form (temporal organization) over content.
That's a nice distinction, but in real-life substantive terms there are larger differences to note. Blogs have quickly evolved toward an eye-candy cutesy-one-liner configuration, with a strong focus on ephemeral news of the day and politically polarized rant. Blog culture also exhibits an exaggerated level of you-link-me-I-link-you mutual back-patting (or insert a less polite metaphor here if you have a naughty imagination). That's a good way to improve one's standing via today's search engine relevance rankings, but it likely won't last. Blogs demonstrate how much easier it is to quote and point than it is to think and write.
Wikis, to be equally critical, trend toward zit-ugly supersaturated but uncrystallized stewpots of information salted with opinion. When an argument breaks out, a wiki can turn into something like a cross between ballroom dancing and mud-wrestling. Wikis too often are miniature models of the Web itself --- in Steve Cisler's image, "... like a library where somebody has taken all the books off the shelves, torn all their covers off, and then thrown them randomly on the floor".
Meanwhile, independent of technology and invisible on the seismographs of hit-count popularity, there remains the millennia-old concept of diary: a place to record things worth remembering from one's daily meanderings on this planet, including signs and sighs, fears and failures, dreams and discoveries. When both blog and wiki are long-forgot, there will yet be journals ...