Context is gained from the page’s revisions, links and how it is referenced by and navigated from other pages. Wikis excel at logical context whereas blog excel at temporal context.
Blogs, emphasize form over function over aesthetics. The form of posts in reverse chronological order and blogrolls constricts possible uses and design. Sure many a blogger has tweaked their template and design to achieve superior ascetics, but they are bound to constraints that if surpassed looses recognition as a blog.
Wiki’s aren’t pretty, but that’s the point. Except in rare instances where design creates function, the more you design the more user functionality you sacrifice.
Wikis emphasize both reading and writing. Sure they could be a little more readable, but that would come at a cost for writing. Costs to be carefully considered for a tool that enables a writable web.
I think I need to take a closer look at Wikis in the context of what I have been writing about the Memex, and my desire to have an outline (a sort of personal directory) for my blog.
Joi Ito’s post has an extended discussion on this topic.