Today, Facebook celebrates the 6th anniversary of the launch of Facebook. While the exact date of the founding is not exactly clear (since Mark Zuckerberg and eventually the co-founders were hard at work developing the site before it launched) it marks a major milestone for the company which grew from a dorm room to one the world’s largest communication tools, reaching over 375 million users every month.

We’ve been following the company for almost three years now and in that small time, the company has built a mini-economy around their service. In the past year Facebook has gone through some major milestones with Facebook Connect and has announced plans to launch the Open Graph API, a service that extends the Facebook Pages product across the web.

While Facebook has yet to find a breakthrough growth model, it has become clear that the company has been shifting some of its focus away from performance advertising to its new Credits platform, which is expected to launch for all developers in the coming months. Many are speculating that Facebook could increase their revenue by upwards of $300 million this year through the Credits platform.

While we’ve posted more conservative estimates of around $100 – $150 million, it’s clear that virtual goods could become an increasingly large business for Facebook. For the time being though, it appears as though Facebook continues to be focused more on growth over dramatic profitability, something many outsiders continue to criticize.

With DST providing many investors with an opportunity for partial exits, there aren’t too many insider complaints as Facebook continues to pursue (and accomplish) the task of becoming the largest digital identity provider. All we can do at this point is continue to watch as Facebook continues its rapid user acquisition and subsequent colonization of the internet. With 175 million users around this time last year, Facebook has more than doubled and appears to be continuing its growth. Happy birthday Facebook!