Flash mobs, participants in an event in which a group of people are organized via some form of telecommunications, assemble suddenly in a public place, perform an unusual and sometimes seemingly pointless act for a brief time, and then disperse. A recent phenomenon synthesizes the activity of flash mobs and street gangs. Communities everywhere have experienced the negative effects of street gangs, and their proliferation has led to an increase in destructive crimes in the United States. A flash gang is a group that uses a social media connection to invite participants to a time and location where they commit a crime and then they split up. Local law enforcement needs to examine response policies to prepare for this new and dangerous phenomenon. Recent protests in the Middle East and North Africa were coordinated using similar strategies, spotlighting the power of using social media technology to oppose government action. The spontaneity and secrecy of the flash mob combined with the targeted crime and/or violence of the street gang produces a mix that is hard to combat even with inside intelligence. The instant access and extended reach of mobile phones and social media sites like Twitter and Facebook bring a twist that makes the spontaneous volatility even more difficult to prevent. (Published Abstract)