The flash mobs of Chicago

There are flash mobs, and there are flash mobs.

Social networking was behind the “good” (if overdone) flash mob in which people are encouraged to meet at a specific landmark and do the flash mob thing.

Like this in Chicago, for instance…

But there’s a new flash mob in town — a bad flash mob. Chicago has recently been hit with gangs of teenagers using text messaging and social networking sites to coordinate attacks on retailers and individuals, according to Crain’s Business.

Saturday evening’s flash-organized assaults in Streeterville, in which a group of young men robbed and beat five people along the lakefront and near Northwestern University’s downtown campus, have brought renewed attention to the groups of roving teenagers who, abetted by social media and text messaging, wreak havoc in the city’s upscale, tourist-heavy areas. Two of the victims were doctors attending a medical conference at McCormick Place.

Mayor Rahm Emanuel says Chicago’s reputation as “a safe place to live in work” is being undermined by flash mobs. Mobs of people have been pushing people off their bikes, the Chicago Sun Times reports, and people have been warned not to ride bikes near the waterfront anymore.

Chicago police are reportedly spending more time on social networking sites to try to figure out when and where the flash mobs are going to attack.