I have a mixed feeling about twitter: I like it as a news and articles aggregator. Many interesting people are active there. But I dislike it because many unsavory people are active there.
And being active on twitter usually means people read your stuff, even if only in passing. Of course, there are many caveats to this assumption, but it is roughly accurate, and it becomes ever more accurate as the person (unsavory or otherwise) becomes more active.
That means there is no gradation between, say, a university professor and some random dude. As a matter of fact, from my experience, they both interact on equal grounds and whoever can mobilize more their audience wins — whatever that means, to win something on twitter. sigh.
Of course, to many this is simply a dream come true. The actualization of democracy on a quasi real world — yet quite real, because somehow it does have impact on the real world. But to me this is the feature I most dislike about it. Virtue, wisdom or plain common sense have no importance on twitter.