It comes as no surprise that Facebook appears to be reaching saturation in its country of origin, as the massive social network now counts just over half the U.S. population as members. But this slowing growth rate makes it all the more urgent that Facebook monetize its existing audience more effectively, especially if it is to support the huge valuations assigned by analysts and private investors.

Social media has all kind of interesting but unexpected applications, including law enforcement, where online technology helps leverage the most important resource for police work -- cooperation and information from the community being policed. This week the Philadelphia Police Department unveiled a new crime-fighting initiative using social media called "Video Villains" -- a "most wanted list" comprised of criminals caught in the act by video surveillance cameras (including both property and violent crimes).