Twitter - like many emergent genres of social media - is structured around networks of people interacting with people they know or find interesting. Those who are truly performing to broad audiences (e.g., "celebs", corporations, news entities, and high-profile blogger types) are consciously crafting consumable content that doesn't require actually having an intimate engagement with the person to appreciate. Yet, the vast majority of Twitter users are there to maintain social relations, keep up with friends and acquaintances, follow high-profile users, and otherwise connect. It's all about shared intimacy that is of no value to a third-party ear who doesn't know the person babbling.
This past February, as one of the keynote speakers invited to contribute to a lively forum sponsored by the Harvard Initiative for Learning and Teaching (HILT), I presented a bold challenge to my fellow professors that has since been quoted many times: “If we can be replaced by a computer screen, we should be.” Some were very alarmed at this statement, assuming I meant that all future learning should be online. But that wasn’t my meaning at all.