According to an article in Mashable, Facebook will reach 1 billion users before the end of 2012.
Facebook currently has 901 million active users, up 56 million since the start of the year! Other staggering figures quoted in the article are “that its network receives 3.2 billion comments per day and 300 million new photos daily. The site also claims 125 billion friendships.”
Twitter is also gaining massive popularity with 500 million users, though only 140 million are acive.