Why Twitter Hasn’t Failed: The Power Of Audience – Interesting TechCrunch analysis (I didn't know TechCrunch did analysis, I thought they just did news) on what makes Twitter work. I'd agree with a lot of this.
Twitter works and enjoys such strong attachment because it provides real-time access to a well-defined audience. The backlog of all previous tweets is a guarantee of permanence (you can even search it) and you can catch up on it anytime. As a result, people use Twitter because they have an idea of who will see their lightweight messages and this sense of audience is reinforced by @replies, re-tweets and references in future conversations (online and offline).
Designing for the sense of Audience is a powerful tool to create cohesion and a sense of utility among users of a service. This lesson from Twitter can apply to many other services too. But before leaving the current discussion, it’s helpful to look at a service that has missed the full power of Audience so far.