According to a study in late 2012, police are no longer skeptics of social media, as evidenced by the various departments that have implemented social media tools to help them fight crime.

In Philadelphia, for instance, the Police Department has used Pinterest to help catch criminals; the Seattle Police Department has instituted a Tweets-by-Beat service on Twitter; and in Cambridge, Mass., local law enforcement implemented a similar service in which auto-tweets mimic the police scanner to inform residents of police happenings.

And the following infographic, courtesy of BackgroundCheck.org, gives even more insight into how law enforcement uses Facebook, Twitter and YouTube -- the most used social networks -- and what percentage of agencies at the state, local and federal levels use the tool.