When I read Tim Bray's suggestion that blogs and wikis couldn't be more different in their essential nature, I knew I wanted to say something on the matter. Well, I've finally got around to it.
Bottom line is I agree with Tim. This may surprise some readers given I've talked before about this site being a wiki/blog hybrid and I describe Leonardo as a wiki/blog server. But here's why I don't consider it a contradiction...
Firstly, purely from the perspective of implementing the content management, there can be similarities—that's what I meant when I talked about wiki/blog hybrids. But Tim was talking about essential nature, not implementation details.
There are really a number of facets to the wiki nature. Four that immediately come to mind:
I'd like to suggest that you can have varying mixes of these and, depending on which mix you have, blogs seem further apart from or closer to wikis.
The important characteristic for something like Wikipedia is the first one. While the rest are still true to varying extents, they aren't what's interesting about Wikipedia. Martin Fowler's bliki, on the other hand, clearly doesn't have the first characteristic. However, it is strongly driven by the fourth and I think it is this facet that really makes his blog wiki-like.
I call my site (and any site served by Leonardo) a "personal wiki" in that it shares characteristics two, three and, to a small degree, four. Plenty of blog software supports in-browser editing. For someone that associates in-browser content editing with wikis, that blog software is wiki-like.
Would two and three alone really be enough to be considered a wiki, though? If not, then wikis and blogs start to diverge. Perhaps people that think blogs and wikis are similar are focusing on two and three. The more you consider four an important characteristic of wikis, the less wiki-like blogs seem—unless they are written like Martin Fowler's. The first characteristic is the one that really sets wikis and blogs apart.
There is no doubt that both wikis and blogs are social. But they are a different kind of social. Blogs are conversations (at least collectively). Wikis (when focusing on characteristic one) are collaborations. Conversations and collaborations are not the same thing. Both are useful—but they are not the same thing.