…we can identify that the real-time Web…

1. is a new form of communication,
2. creates a new body of content,
3. is real time,
4. is public and has an explicit social graph associated with it,
5. carries an implicit model of federation.

One consequence of the 140-character limit (and a key reason why the real-time stream is so easily adaptable to other uses) is that messages are largely atomic in nature. Each refers to an individual item: a thought, link, event, product, person, or company. They also typically contain some evaluative or emotional component, such as “Look at X because it’s cool or interesting” or “I support Y” or “I disagree” or “this is no good.”

This discrete nature of Twitter messages means that items, and the sentiments attached to them, can be extracted and then aggregated, allowing us to measure the activity being generated around a particular subject and, in some cases, the general feeling about it. This is not unlike the way buy-and-sell orders signal interest in a stock; but in this case, any popular subject matter can be tracked. In combination with other factors, this discrete nature and emotional component allow for some interesting usage and applications.