...comments, David Galbraith: "To add comments within someone else's weblog is surely a retrograde step? In true trackback style the comments box should pull up a list of references to the post from Technorati - with a box that posts to your own blog or signs you up to start one."
I've had this same thought before. But I also think it's potentially geek-centric and only good in theory. For instance, a Trackback reference is not the same as a comment. Distributed discussions are awkward. And if a book club has a blog, talking about their reading, the most natural thing is to make comments on other people's posts, on the blog itself.