While I agree that a lot of mainstream media articles miss the mark, I think that this piece, too, defines blogging too narrowly. (Though I think it makes a bunch of interesting points.) The term "blog" used to refer specifically to a place to post links-plus-info, a la boingboing, but these days I often see the term also used to refer to personal online journals, many of which rarely use links and don't invite discussion.
And conversely, there are plenty of systems that use reverse-chronological order (versiontracker, various news and rumor sites) that aren't what most people would consider blogs.
So although this article presents some interesting ways of looking at blogs, I don't think it quite captures a precise definition of the essence blog nature; or perhaps I merely mean that the definition of the term "blog" is changing over time, like most definitions.