Twitter is not the new Facebook/MySpace/Hyves/StudiVZ/Hi5/Bebo/whatever.
Twitter is not a newspaper, nor is it place for in-depth journalism.
Twitter is not a “real” microblogging platform (if you see a blog as a place where a person (or more) write blogposts that you can comment on – Jaiku is a real microblog then).
Twitter will not be mainstream in the sense Facebook is. It could be mainstream in the way Blogger or Wordpress or Movable Type is.
What is Twitter then?
Twitter is a place where I follow people I find interesting and learn something new about stuff that interest me.
It is a place where eye witnesses can tell what is happening at any given event as it happens.
And it is a sleeping hivemind I can wake up when I need an answer with more context than Google can give me.