The majority of consumers worldwide will soon have smartphones. Smartphones are about the most important thing to happen to social networking since Harvard sent its acceptance letter to Mark Zuckerberg.
Smartphones know where you are, who your friends are, who's nearby, and soon thanks to NFC, they'll know what you're buying and where. They are the key element of the next, mobile phase is social networking.
Facebook is the power hitter in social networking today, and is likely to drive the most activity and a fair share of the innovation in social networking in 2012. But it's not the only company driving things forward. Google+, Twitter and Linkedin is also in this business.
Facebook is serious about mobile social networking, but it is not the leader in this space in terms of design or technology. Smaller companies, like Path and Milk (with its first app, Oink) are coming out with new takes on mobile interaction. Square could play in this economy as well. All these services will likely use Facebook's network to put people or businesses or in touch with each other in new ways. More specialized mobile networks (really riders on top of Facebook) will appear this year.