Nothing in the history of communications compares to Facebook's rise. Cellphones and the Internet took a decade or more to engulf the world; Facebook did it in three years.
On 1 January 2008, Facebook's non-U.S. audience, according to the Facebook tracking firm Inside Facebook Gold, numbered 34 million people. Three years later, there were 350 million non-U.S. Facebook users—a tenfold increase.
Iceland—and its tiny but highly educated population with, apparently, plenty of free time—technically wins the gold medal for the world's most Facebook users per capita. But another 500 million people live in countries where half or more of the population—not the online portion of the population but all of it—are on Facebook.
Already today, in roughly a third of the world's countries, Facebook penetration is over 25 percent; overall, more than 10 percent of the world's population have active Facebook accounts. By next January, about 16 percent will.