Just five months ago, Facebook announced it had 400 million monthly active users worldwide and this week it plans to announce 100 million more.
The company has launched "Facebook Stories," a site within Facebook, to celebrate the 500-millionth-member.
It will enable users to submit stories about the social network in 420 characters or less the same as a typical Facebook status update according to All Things Digital's BoomTown blog.
As Facebook continues to grow, Inside Facebook a site which analyses Facebook usage said it is possible for it to reach one billion users worldwide, if it focuses on less Facebook-saturated countries like Russia or South Korea.
However, in some European countries and the US, Facebook has become so popular there aren't many users left who can join, Inside Facebook said.
Still, it has not found consistent patterns of decline overall and countries with higher popularity still tend to grow.
Facebook chief executive (CEO) Mark Zuckerberg is set to do a public interview tomorrow with ABC News' Diane Sawyer and rumours suggest he will confirm the increase in users, as well as what it could mean for the future.
