Over the past week I’ve been dipping into the flood of “tweets” pouring out of Tehran. And I’ve been impressed: primarily, of course, by the spirit of the Iranian people, but also by the way Twitter has kept me informed with an immediacy and rawness that mainstream media coverage can’t match. What we’re seeing in the east is a landmark event, not only in geopolitical history, but also in the history of the internet

But while Twitter has undoubtedly played a major role in events, there’s a technology which I think has been even more pivotal. I’m talking about camera-phones — such as the one that captured the last living moments of a young Iranian woman named Neda, shot dead during a protest on Saturday in the streets of Tehran.

The shocking footage has quickly propagated around the web, arousing horror and outrage in Iran and across the globe. Without a doubt it’s given the protests new fuel and new focus: I’ve seen more than one Iranian Twitterer describe Neda’s death as the turning point that persuaded them to join the uprising.

Interestingly, though, it’s been unofficially estimated that on the day Neda died, over a hundred other protesters were also killed in Iran — yet no one’s rallying around them.

Partly, of course, that could be because Neda was a young woman, who appears to have been acting wholly peacefully when she was murdered. It’s easy to get angry about her death, while with other protestors we simply don’t know the circumstances.

But that’s the important point: we don’t know, because however tragic the other deaths may have been, they weren’t captured on video. We can only ever know of them at second hand. And for that reason they’ll never provoke a reaction as visceral and emotional as what we feel when we actually see the life slowly fade from Neda’s eyes.

Clearly, it’s impossible to say what will happen in Iran over the coming days and weeks, but the protests don’t seem to be petering out — if anything, dissatisfaction with the regime is growing. With a general strike now brewing alongside continued unrest we could conceivably be heading for a major shake-up of power in Iran.

And any success the protesters achieve will have been made possible not by external influence — but by the camera-phone, and the incredible rallying power of a humble video file.