Blogs and Wikis
Krzysztof Kowalczyk makes an argument for bundling a wiki with a blog. I agree wholeheartedly with his endorsement of wikis. I've used a few, and installed two of them myself, and I think they're terrific. But I don't think that wikis should be bundled with blogs (especially WordPress) by default.
First, blogs and wikis serve different puposes. Wikis can be used as a publication engine -- see the Wikipedia as a perfect example -- but the kind of thing you'd publish on a wiki is fundamentally different from the kind of thing you'd post on a blog. The power of wikis is the interconnectedness of all the data: you're only one click away from any other page on the wiki. That's why a wiki makes perfect sense for an encyclopedia, or a knowledge base, or random notes collections. Blogs have a certain interconnected-ness, what with trackbacks and pingbacks, but blogs impose more continuity ... my comments here will be linked to Krzysztof's site; but if someone else blogs their response to my comments, the connection won't be passed on to Krysztof automatically (unless the blogger specifically elects to trackback or pingback him as well as me). If someone uses my comment form below to comment directly on this post, Krysztof will never know unless he comes to visit. Blogs have a linearity to them that wikis don't.
Second, blogs have an implicit power structure that results from the limited selection of authors. A blogger chooses who posts top-level entries to his blog, restricting everyone else to mere "commenter" status. Commenters rarely get the ability to edit their comments; the blog administrator(s) have the sole power to edit or remove comments. The power structure ensures that a blog's readers are always in the position of respondent, and never initiator. In order to initiate, one must control their own blog. Wikis are completely different, though, because (usually) anyone can post and edit. Wikis level the playing field a bit, because any visitor can create new directions for participation. Visitors can correct their own comments, as well as correct the comments of others. Instead of one-to-many communication from a blog, wikis support many-to-many communication, where all participants are authors, editors, and readers. Although the wiki administrator still has absolute power, and wikis can be configured to restrict who can post, constraining wiki operation in this way vastly limits the utility of the software. If you're denying wiki features to people, why use a wiki at all?
Third, wikis lack much of the distribution conveniences of blogs: syndication feeds, trackbacks, and pingbacks. To really use a wiki, participants need to go to the wiki. A blogger can read aggregated blog entries in a feed reader, then post replies to an entry on her blog and alert the source that she's responding (trackback or pingback) without ever visiting the source blog. Blogs allow conversations to be carried out while maximizing each participant's convenience because blogs are predominantly one-to-many publications. Blogging in aggregate approaches many-to-many communication, but there's a lot more infrastructure involved to support that. Wikis gracefully support many-to-many communication by constraining the necessary infrastructure: the wiki is the hub through which all conversations are routed.
Integrating blogs and wikis probably doesn't have much appeal to too many people, since blogs and wikis really serve different purposes. The kind of people who want to use a wiki will largely be able to do so (or figure it out) for themselves. Integrating wikis within a blog package unnecessarily complicates the core package, increases support requirements from the development team, and may possibly bloat the package with features that people don't use.
(hat tip: Blogging Pro)