Twitter may be pushing 10 billion tweets, but Facebook has reached $1 billion in revenue, according to a recent article on TMCnet.com, written by David Sims. Citing a Mashable.com feature, Facebook’s finance numbers have always been hidden  away. But,  recently additional tidbits of information have been leaked, which illustrate a rapid increase in revenue over the last few years. In 2007, annual revenue was said to be  at $150 million. Revenue for 2008 was believed to be at $300 million, while it is widely cited that the social networking behemoth pulled in roughly $700 million in 2009.

But, where is the boost coming from? Thebigmoney.com says the recent, rapid growth is due to, “…a strong advertising push from social gaming companies, along with direct marketers and local businesses.” While there have always been a number of theories regarding the site’s (in)ability to monetize, its registered 400 million users presents an unparralled opportunity. And, if Facebook can figure out a way to successfully grow its revenue, this could pave the way for monetizing other social sites and apps. At the end of the day, Facebook’s revenue will overwhelmingly come from advertising. But how the story will continue to play out remains to be seen.

Via TMCnet