Both essays are largely "masses of metablogging"--that is, blogging about blogging--with a healthy amount of commentary and synthesis. The earlier essay (which, if you hate PDF and don't mind crude HTML, is separately available here), discussed blogging as a median medium: a sweet spot in a casual media hierarchy of length, thought and formality.
After that discussion (which I think many of you will find interesting on its own merits), there's a lot about comments and conversations as these relate to blogs, followed by a discussion of whether blogs are "here to stay." (You might want to page over to Page 17 in that issue, Library Access to Scholarship, which includes a fair amount of back-and-forth on whether professional journals should evolve into blogs.)
And in Part 2...
This time around, the focus is "why"--but includes a digression on anonymous or pseudonymous blogging and whether such practices weaken the contributions of such blogs to the professional literature.
That discussion takes place within a section on archives and archival blogging. That's followed by some notes on Andrew Sullivan's "Why I blog" and some reactions to that article (decidedly not a post!).
"Why academics should blog" follows, including a variety of perspectives from academic librarians and other academics and including a striking discussion from John Dupuis, "If you don't have a blog you don't have a resume."
I think you'll find a number of useful insights--and a notable lack of Everybody Must Have A Blog thinking. If you hate PDFs or prefer crudely-formatted HTML, the article's available as a separate.