Citizens may object to their social media mining by law enforcement, but the practice can keep the public safe.
Police departments should continue to monitor social media to inform law enforcement. After all, social media sites are full of data that can make police interventions more effective, from posts about crimes in progress to damning evidence offered freely by criminals and even live videos of crimes. However, in designing these initiatives, police departments need to pay closer attention to the Constitution as well as the needs of citizens.
Source: Why Police Should Monitor Social Media to Prevent Crime | WIRED