According to insidefacebook, the social site Facebook is on track to eclipse $1 billion dollars in revenues this year. That’s one billion, with B!

Since the company is private exact figures are not available – at least not to me – but Insidefacebook estimates Facebook’s 2009 revenues in the ballpark of $600-$700 million, well above the $300 million range from 2008.

Much of Facebook’s revenues comes from advertising with half of that coming from their ad platform. Facebook ads are still in its infancy when compared to Google Adwords and it pales in usability and efficiency to Google’s. But if improvements continue it may challenge Google down the road as the top ad platform on the net.