The first flash mob took place in New York in May 2003 and quickly spread to Europe, with the first UK event taking place last week when 200 people met up at a London furniture store, admired the sofas and disappeared, much to the bemusement of store manager, Derrick Robinson.
He admitted later to the BBC, "My first reaction was I thought there was a fight. Then I thought it was a celebrity". He is not complaining though – the resulting press coverage has more than made up for it.
The bizarre events are usually kept secret, with directions and instructions being given to participants right at the last minute. Previous examples include a mob tweeting like birds and crowing like roosters in Central Park, or gathering outside the American Embassy in Berlin – to drink a toast to 'Natasha'.
More UK events are planned, the next one being in London on 22nd August, with another in Edinburgh on 28th August.
But organisers of the events are not blind to other forces using the phenomenon. US site cheesebikini.com warns participants, "remember that a corporation could easily create fake flash mobs designed to spur more business to its retail outlets. Don't be a sheep!"
And protest groups are already considering how best to integrate flash mobbing into their strategies. Inevitably this will have an effect on how flash mobs are regarded from a legal and police enforcement point of view, and it may be that event organisers will soon find themselves forced to obtain permits, as is required for the more familiar type of public assembly – the march.
To date there seems to be little enforcement action taken with regard to flash mobs, other than a police presence, but this is expected to change. The first sign of increased police interest came recently in Toronto when an event had to be cancelled as the media and police presence outnumbered the mob itself.