Jeff's comment about the evanescence of blogs intrigues me; no question that my challenge is to keep from hoarding piles of stale blogs -- start a blog, write a lot, start another blog, write a lot. You get the picture. The endurace of an interface like Tapped In has something to do with the richness of the interface and its polysynchronous nature and the human (oh my gosh!) presence. Although blogs offer a range of interactivity (hyperlinks, comments, blogrolling, RSS feeds), all interactivity remains asynchronous.
Blogs hook me cuz I write and I teach writing. Audience & publication are two areas I'm investigating, particularly with my advanced comp. class and blogging there.