With a global user base approaching 500 million people FaceBook is positioned to dominate the mobile social app space. Anyone building apps with a mobile component needs to consider the integration of FaceBooks new mobile Open Graph as well as other ways to leverage FaceBook's user base.  Having a good grasp of how to use FB's location API is going to be critical.

Eric Tseng, head of FaceBook's mobile products recently spoke at MobileBeat 2010 in San Francisco.

Facebook has about 150 million mobile users, up from just 100 million in April, and is counting on cell phones as the key platform for the future, according to the social-networking giant's head of mobile products, Eric Tseng.

That's 50% growth in just a couple of months.  And yes, those are millions of user.