JBroll
I MIX WITH PHYSICS!!!!
I know of it, mainly because of the urban legend (claiming that the sign originated after threats involving crippling England's longbowmen at the battle of Agincourt), but I'd guess that, like everything else that's popular over here, some asshat started doing it and everyone else followed for no damned reason apart from an uncontrollable urge to do something fucking stupid every second of the goddamned day.
Jeff
Jeff