Not to sound flip, but my programmatic experience with Twitter, leads me to believe most of it seems to be one big botnet. Do any largish API crawl of Twitter and you'll be amazed by the large % of inactive accounts or non-sensical accounts (which I assume to be bots)

My personal experience (where I mostly follow news organization feeds) is different.

In short, in my experience it seems Twitter is great as a broadcasting medium and not so great as a two way communications medium.