At the Mobile Beat conference Eric Tseng, head of mobile products for Facebook (and former Google-Android exec.), announced that Facebook now has 150 million "active" mobile users (that means daily usage). That's up from 100 million in February.
Against that backdrop there are indications that, at least in the US Facebook's growth, may have slowed. The company however sees mobile as a driver of its next phase of growth. Overall, there are more than 500 million Facebook users globally.
Tseng suggested that Facebook would soon become a "mobile platform." That means that Facebook will be extending "the social graph" to third party applications and sites. The Open Graph API and the Like button will also make their way into mobile according to Tseng.
Facebook is poised to roll out some sort of location-based service. Its exact form is uncertain. I've argued that instantly Facebook would be a huge mobile ad network should it decide that it wants to become one. Yet there are reasons to believe that won't happen in the near term.
Facebook's forthcoming Q&A service is also one that could be a potent location-based recommendations engine. And the Like button data will be a huge source of local favorites and recommendations. Third parties will be tapping all this data to enhance their apps and sites.
The company sees mobile devices as a growth engine party because in developing countries (e.g., India) mobile is the primary (and maybe only) tool for Internet acces. This is why Facebook developed its SMS-based "0.facebook.com" site earlier this year.