Way back before twitter was hyped on TV, before it was big, it was being talked about in the RubyOnRails community, since it was a new site that used Rails. And so I saw it before the hype, though I didn't sign up. Actually, when I first saw it, you didn't even have to sign up, it was just some sort of unannounced beta. And it wasn't "microblogging" or whatever. Instead, it posed a simple question: What are you doing right now? And you were supposed to answer in less than n characters. And everybody was like, "huh? Wtf is this for?" They still don't really know what it is for. It is a communication medium that actually managed to promote the tagging of comments in a way that causes users to use tags.
Impressive, whatever it is. Though we had public communication and subject tagging even in the 80s on the BBSes.