"If you're down for making money, we're about to go hard in east London," one looter messaged before the violence spread.
Still others direct looters to areas of untapped riches stores selling expensive stereo equipment, designer clothes, alcohol and bicycles.
Most show a portent of even worse things to come. Encrypted messages sent via BlackBerrys are being used by mobs to encourage rioting across Britain mayhem born of an incendiary mixture of conditions that converged during Europe's sleepy summer vacation season.
Many of the masked or hooded youths have been photographed typing messages on their cellphones while flames engulf cars and buildings.
Conditions have been perfect for the unrest. Britain's economic outlook is bleak, youths are out of school and unemployed, police ranks have been depleted by summer vacations, and social media sites coupled with dramatic video of the rioting have bolstered a mob mentality and spread disobedience.
BlackBerry's messaging system is popular among youths because it's free, compatible with multimedia and private, compared with Facebook and Twitter. Its encrypted messages give troublemakers an added benefit: Police aren't able to immediately trace message traffic the way they can with regular cellphones.
Social media have been a potent force in fueling the riots that began Saturday in London's boroughs and later spread to other cities such as Birmingham, Liverpool, Leeds and Bristol. Messages have also been sent via regular texts and on Facebook. One 16-year-old boy was detained Tuesday for allegedly encouraging violence on Facebook.
But the social networks also have provided refuge for fearful residents and shop owners who say police efforts have been feeble and slow. Twitter is helping to pinpoint areas of violence, organize community cleanup groups and alert people of alternative routes they can use.