TVH mentioned in my comment section about "left-wing echo chambers", and named off a few left-wing sites/blogs. Needless to say, he's missing the point.
The "Echo Chamber", at least in the way I refer to it, is the reinforcement effects of dozens and dozens of bloggers saying the same thing; they reinforce their own beliefs through the constant repetition and agreement. There's no way left-wing blogs (or even sites) can possibly do this, because the rightist juggernaut is always there to throw it off. Look at TVH's own site; MWO has a "watch" site already, and why is that? There are dozens of other, equally strident right-wing sites that do pretty much the same thing... do they have watch sites? Libertarian Samizdat is both big and ideological... does it have a watch site? (The name of a site is a misnomer.. there's nothing "subversive" about libertarianism online. Far from it).
As I've been saying since my first entry, there is a severe imbalance in the relative prominence of right-wing vs. left-wing commentary over a variety of different media, and the mythical "left-wing" journalism that right-wingers are always complaining about doesn't change that. I think half the reason MWO is so scary to so many people is because it bucks the trend, and watch site aside they can't really score a hit on it or even label its anonymous proprietor as some sort of leftist extremist. That's nice, but it's not parity.