"Blog Friends and equivalents let me know what a person’s surfing, Facebook mini feeds show me what someone’s sharing, there are many social bookmarking tools and RSS readers available, there are even shared readers available.
But so far none of them gives me this kind of information as succinctly as Twitter. Now of course the value didn’t come directly from Twitter, it came from Halley. I know Halley. I know she reads a lot. And I trust her opinions, without having to agree with all of them. And when she says “Best thing I’ve read all week” I sit up and take notice. I take a look. I wander over to where she points."