Twitter isn't the new web. But it is a model which reveals the special things that happen when you can break beyond your usual circle of friends. It's fuzzy-edged, adhoc, self-forming communities of purpose are why the average number of followers is already 250 (compared to Facebook's 125 average friends per person).
It introduces you to more people and more stuff you didn't know you needed to know than anything I've seen yet.
It's not the end of the story. Expressing and matching your metadata with the expressed needs of others, in real time, beyond even the silo of twitter, is where we are headed.
But don't let anyone tell you twitter is just another 'social network'. It matters not whether a more fashionable alternative emerges. What matters is that twitter has set the benchmark and revealed the value of fuzzy edges.
Enjoy the above illustration. It's from Manolith.com