The unfolding of the #iranelection protests over the weekend has been a coup for Twitter, mostly because the tweetosphere was the channel through which the best information about the election (theft) aftermath was emerging. The now-famous Saturday CNN fail further emphasized the advantage tweet-based news-gathering holds over the oh-so-80s stringers, reporters, cameras, and satellites paradigm: immediacy, agility, redundancy, and authenticity. So it’s settled then, Twitter was on fire while CNN was re-running an inane Larry King interview with some meathead from American Chopper. Twitter succeeds where old media fails.

Well, no. Here’s why: Twitter aggregates the observations and opinions of people who tweet. Sometimes people who tweet have something to say that isn’t getting heard, like when their government cracks down on old media. But all social media is subject to structural biases. Obama dominated Facebook last November because his campaign benefited from broad social and cultural – in other words, structural – affinities with the medium. Ahmadinejad supporters simply don’t tweet, so in a Western mediascape where Fareed Zakaria is  a day late and a source short, we hear from the reform-oriented, urban, iphone-wielding (SMS was blocked so most tweets were coming through smartphone apps) intelligentsia.

When re-tweeting replaces reporting – whether because newsrooms are slashing their foreign bureaus or because a cabal of mullahs are restricting  media – structural biases are ignored. Mousavi’s supporters took to the streets by the hundreds of thousands yesterday; their voices deserve a medium that can penetrate the theocracy’s digital curtain. But how can we claim we’re witnessing the triumph of disintermediation when the only sound we hear is a chorus of tweets?