It all kicked off with Paul Chambers. Remember him? The 28-year-old trainee accountant who, frustrated at the closure of Doncaster's Robin Hood airport due to snow, jokingly tweeted about wanting to blow it up ("You've got a week and a bit to get your shit together," he deadpanned, "otherwise I'm blowing the airport sky high!!") only to provoke a spectacular sense-of humour failure on the part of the authorities, who convicted him of sending a menacing message under the Communications Act 2003. When he lost an appeal against his conviction back in 2010 (he's now taken his appeal to the high court), a solidarity campaign exploded on Twitter: at the suggestion of user @christt, who wrote, "I think we should all tweet Paul Chambers' original joke, Spartacus style", around 4,000 users copied Chambers's message under the nifty hashtag #iamspartacus, evoking the stirring image of hundreds of Roman slaves standing up for Kirk Douglas.

The defiant gladiator is continuing to make his presence felt. Last month, a group of disability campaigners launched a report on the government's proposed reforms of the Disability Living Allowance under the hashtag #spartacusreport; what might have remained a minority-interest campaign quickly acquired extraordinary momentum. A number of high-profile tweeters – including Stephen Fry, John Prescott and Billy Bragg – picked up on the hashtag.

And on Wednesday, there he was again: back as #iamspartacus this time, as hundreds of NHS doctors and patients took to Twitter to express their opposition to Andrew Lansley's controversial healthcare reform bill, and solidarity with Professor John Ashton, the senior doctor who has been threatened with disciplinary action for signing letters critical of the changes. "Gosh!" tweeted the doctor and Bad Science columnist Ben Goldacre, "if you want to see the power of a hashtag take a look at #iamspartacus about the #NHSBill."