A simple Google search will lead you to find hundreds (or even) thousands of news stories where stupid Facebook updates have led police to the capture of criminals. These stories range from parents thinking a picture of their baby pretending to smoke from a bong is funny to the arrest of a mafia hitman who was so update-happy the FBI were able to track his GPS.

A recent article by CNN looked at a pioneer in the emerging area of collecting criminal information from social media websites. It's becoming a big thing the city of Cincinnati. They are collaborating University of Cincinnati's institute of Crime Science to further understand how to search for and collect information. They started small, like many departments, and had a few officers who would look for and make note of possible criminal activities. However, it wasn't until the collaboration that things really took off. By working with social-media experts, they were able to learn how to more efficiently search for information. This information (such as a known criminal's friend list) was then placed into a database, which was then able to be cross-referenced against known criminals and records. Officers quickly learned that Facebook was being utilized to set up drug deals, brag about crimes, and even as a place to share videos of criminal activities.
Although the judicial system is still largely playing a game of catch-up with the advances in technology. However, warrants are available for the official collection of online data from all of the social networking sites out there...and that allows for the appropriate chain of evidence for the information to be utilized in court.
If social media is going to be a means of mass communications among criminals, departments across the country are going to have to become knowledgeable of how to search and acquire that information as well.