WHEN FLASH-MOBS GO WRONG: Oops. “A spontaneous musical concert at a California shopping mall ended with the entire complex being evacuated after some 5,000 people turned up to sing. The incident happened at the Roseville Galleria shopping mall, which is reported to have started shaking due to the volume of people inside. . . . As they burst into song, there were reports that the building’s floor began to move and creak, and witnesses reported hearing popping sounds. Emergency services were forced to evacuate the entire building.”