Wikipedia isn't intended to be anchored in the perspectives of a single person's views; in the ideal case Wikipedia is supposed to be completely neutral. Even if one's blog is more wiki-like, the owner would necessarily be associated with those perspectives and topics and interests.
I suspect that in many cases, a blog-wiki wouldn't be terribly useful; there simply aren't enough interested readers to do much (though I've had many people point out simple corrections on my own blog). But in certain circumstances, a blog-wiki could be very interesting. One could imagine that the blogs of particularly prominent personalities could take on lives of their own.
Actually what Paul is proposing isn't new - see http://en.wikipedia.org/wiki/Bliki. It looks like the idea hasn't really hasn't taken off in the purest form, where anyone can edit a personal blog.
I suspect that in many cases, a blog-wiki wouldn't be terribly useful; there simply aren't enough interested readers to do much (though I've had many people point out simple corrections on my own blog). But in certain circumstances, a blog-wiki could be very interesting. One could imagine that the blogs of particularly prominent personalities could take on lives of their own.