Five hundred million people “are now using Facebook on a monthly basis,” PC World reports, which means “Facebook has a slightly smaller population than the continent of North America,” and that’s “enough users to put 75 people on every one of the over 6.6 million square miles of Russia, the largest country in the world by landmass.” Just a couple of PC World’s “Fun Facts,” and this is just one of nearly 800 such news reports worldwide, linked to from Google News as of this writing. A Wall Street Journal blog reports that 1 in 40 FB users are in India. According to the San Jose Mercury News, “if Facebook gallops ahead at its current pace, the 1 billion mark would indeed be reached in 2011.” Founded at Harvard in 2004, FB “went from zero to 250 million users in five years — and doubled that number over the past 12 months,” the Mercury News adds. Facebook is celebrating this milestone with a new app called “Facebook Stories.” You can read about it in the FB blog here. Users can also share their Facebook stories here.