The more interesting property relates to subscription. Like RSS, you start receiving updates from contacts you've explicitly selected. Spam-proof, and highly conducive to emergent conversations. (If you're a Facebook user, this is kind of like the News Feed.)
Here's another way to look at it: logging into your microblog is like joining an enormous IRC channel spanning the entire world, only almost everyone is set to
This is clearly another case of too many mad scientists, and not enough hunchbacks.