As my esteemed colleague Jerome Taylor reported for this newspaper yesterday, the fastest-growing website that campaigns for social change is coming to Britain. Change.org has helped a 22 year-old nanny juggling two jobs take on Bank of America, forced the Motion Picture Association to adjust a film's rating and, most thrilling of all, helped bring the appalling tale of Trayvon Martin to public attention. When the parents of that murdered 17-year-old couldn't interest anybody in their son's death, they went to Change.org and garnered 2.2 million signatures instead. That's for one petition. The site launches 15,000 every month.

Digital campaigning is changing the world for the better – but in ways that are more complicated than is generally understood. What websites like Change.org and the magnificent Avaaz.org do is raise awareness of some deep injustice or crisis, generate a huge amount of digital buzz, and co-opt an engaged online community into their narratives of progress. I recently spoke to Macon Phillips, Director of New Media at the White House, who has had great success with online petitions. He made clear both how seriously President Obama personally takes these websites, and how their influence is only just getting started.

A central strength of them is that they don't ask too much of their audience. Sometimes campaigning websites do raise money for a particular cause. Avaaz.org is particularly brilliant at this. But generally they have what in techno-speak is referred to as a hierarchy of engagements.

Imagine a pyramid. At the bottom is a vast spectrum of ways to be involved without expending much effort. At the top is a narrower set of ways to get much more deeply involved – donating money, say, or contributing a blog-post, or setting up your own petition.

In an essay for The New Yorker, Malcolm Gladwell cited research by Stanford sociologist Doug McAdam to argue that those levels of engagement explain why "the revolution will not be tweeted". Real political revolutions depend on extreme solidarity and strong relationships between people with shared ambitions, who come together and meet face-to-face. Websites like Twitter and Change.org, he argued, are instead based on "weak ties".

There is something to Gladwell's argument; but why focus on revolutions? Across the globe, endless injustices are visited on the innocent every second. In bringing those to popular attention, shouting about it, and being heard where it matters, the likes of Change.org are speeding up history.

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