Silicon Alley Insider took its best shot at estimating how Facebook brings in money, as the social-networking company has not yet gone public, so it is not required to disclose its financial information.

Sources told Silicon Alley Insider that the company told its investors its 2009 revenues would reach $550 million, up from a $400 million figure the blog received a couple of months ago.

Based on input from sources, Silicon Alley Insider's breakdown of the $550 million: $125 million from brand ads; $150 million from Facebook's ad deal with Microsoft; $75 million from virtual goods; and $200 million from self-service ads.