Random acts of Neknominations.
It started with a #neknomination [well, let's be honest - it likely started with a drunk Australian feeling like this was something he thought was a good idea for more people to do?] an online video'd drinking challenge game where you "film themselves drinking a pint of an alcoholic beverage, usually beer, in one gulp and upload the footage to the web" [wikipedia] and then nominate two other people to do the same, paying it [...]