In 1929, Hungarian author Frigyes Karinthy proposed that there were six degrees of separation between any two people in the world. The theory was made popular by a play, movie and later a trivia game in which players try to link the actor Kevin Bacon to another Hollywood star within six steps. Yesterday, Facebook announced that with its 721 million members, and 69 billion friendships between them, there are only 3.74 degrees of separation between any one Facebook user and another. Researchers summarized it like this: "A friend of your friend probably knows a friend of their friend."
