I have often been told, usually with a certain air of self-satisfaction, that Twitter will not replace the newspaper. (Well, okay, maybe The Guardian.)
This is sort of like saying that rollerblades won't replace the family car. It totally misses the point. Twitter is not destined to be the next iteration of reporting. Or blogging. Or searching the web. Or Facebook. That's a complete misunderstanding of what it does.
Join the chat room!
Twitter's most reasonable analogue, if you must have one, is something like IRC. It's a place where people can come and have a chat in short bursts. The other similar invention of the early web is Usenet. (Of course, both these things still exist; on the web, nothing ever quite dies.)
There are, however, a couple key differences that separate Twitter from its antecedents. First: Twitter is fundamentally open. There aren't rooms or groups on Twitter. The only closed parts of the system are users who make their posts private (in which case, only people they allow can see their feed), and direct messages, which are fairly incidental. If someone tweets about, say, Expression Engine, someone else can search for that and find it. (Even better if they use the hashtag #expressionengine or #ee, which people use to unify all the tweets on a given topic.) Many twitter clients let you run and observe searches like this in near-real time.
The second big difference is that you only see what you want to. Twitter can't be derailed the way IRC or Usenet could. There's no need for moderators. Your main feed is pulled from the people you choose to listen to. If you don't like someone's tweets, you can always unfollow them. People needn't "play nice," because there's complete separation.
That makes Twitter exceptionally useful -- if you're in one of those groups (like web technology or politics) that's adopted it broadly. You end up very quickly coming into contact with people who have the same interests as you, because they're searching for the same things on Twitter, or monitoring particular topics on Twitter that are important to them. It's all a very cool way of making conversation across great distances, and it accomplishes it in a way that its closest relations don't, because of its open, casual nature. All in all, a brilliant invention. life