A great deal has been written about the way in which charities, campaigns and political movements have borrowed the techniques of commercial marketers and advertisers. Very often, however, the marketing profession would do well to look at the ideas that evolve spontaneously as part of political protests. Many are simple, but ingenious.

Mass movements - particularly those which are denied the right to free speech through conventional channels such as television, radio and the press - have increasingly been using the internet and mobile technology to promote their messages. These newer media are, of course, by their very nature more democratic and difficult to censor effectively. Sometimes, however, activists are forced to think more laterally.

Iran has seen a great deal of turmoil in recent months, with a protest against the bogus election results turning, over time, into a challenge to the theocratic regime itself. Low-resolution video footage on sites such as YouTube has given us a glimpse of the brutality of the government forces, while Twitter has played an important part in the dissemination of news. There are two other developments that have particularly caught my eye though.

The first has been the use of rooftop chanting at night to show the strength of anti-government feeling - a form of protest that was used successfully against the former Shah in the 1970s, prior to the Islamic revolution. The second, reported more recently, is the campaign to deface the Iranian currency with protest slogans. As Iran is a largely cash-based economy, this has even greater impact than it would on the streets of, say, London or Paris.

Perhaps this is the ultimate viral campaign? The medium is ubiquitous, as the currency is in constant use and people can't ignore it. The message spreads quickly via retail outlets and market transactions and the notes can find their way into the hands of absolutely anyone. What's more, there's a constant circulation - at least until such time as the authorities can remove the offending cash.

The government's solution currently is to say that 'defaced' notes will no longer be legal tender from January. I suspect this tactic is doomed to failure by the sheer number in the hands of the public and confusion over the status of individual notes. When exactly does a scribble or a smudge of green ink become a subversive political statement? When does a messy note become an illegal one? Generally, if people receive a 'dodgy' note or coin, they always like to kid themselves that it's ok, don't they? And hope that they'll be able to pass it on. After all, if they accepted it as genuine, maybe someone else will?

Next time you encounter a celebrated viral campaign for a big brand, spread via email or social networks, it's worth remembering that messages are probably travelling more quickly and effectively in Tehran on the back of 1,000 rial note.