Valleywag has a helpful chart of the stormy relationship between progressives and Twitter. It reminds me of how blogging developed. At first it seemed to be some kind of monoculture, talking about particular things - and a lot about itself, trying to constitute the environment in the first place. And people thought that "blogger" was an identity; which of course no media can stay, if it is successful as a mass media.
Later we found out that political blogging is more like talk radio than anything else. Really good for fringes on both sides, energizing the troops - less good as an actual agora of public opinion.
Twitter also seemed to be owned by progressives; they built it after all. But of course that doesn't work with mass adoption and now the monoculture there is going the way of that of blogs.