Because the media leaves their parents basement once in a while and notices in every direction in a reasonably populated area that there is either:
a) multiple conversations that the word facebook comes up every 3rd sentence
b) sees someone using their internet connected device (ie - smartphone, Ipad, DSi, netbook, etc) on facebook.
My suggestion is leave the house once in a while.
All these replies from people mentioning events that happened on this day in order to try to invalidate the claim that this wasn't the most boring day in history, and yet none of these are offering any suggestion of which day is a better contender. Please don't just say "this cannot be the most boring day because [insert random event] happened on this day!" and think you are clever without offering a new day which could take its place.