The images have already been so jolting to Brazil's elites that President Dilma Rousseff has convened a meeting of top aides to form a response and business owners have obtained injunctions to shut them down: thousands of teenagers, largely from the gritty urban periphery and organizing on social media, going on raucous excursions through shopping malls. Called rolezinhos (little strolls) in the slang of So Paulo's streets, the rowdy gatherings may be going beyond mere flash mobs to touch on issues of public space and entitlement. Why don't they want us to go inside malls?" asked Plinio Diniz, 17, a high school student who attended a rolezinho this month in Shopping Metr Itaquera, a mall here where police officers used tear gas and rubber bullets to disperse the estimated crowd of 3,000. Unnerved by the street protests that shook cities across the country last year, the authorities are carefully trying to evaluate ways to react to the gatherings, which began heightening in size and intensity in December. Rolezinhos are generally organized on Facebook, with nearly 20 planned in Brazilian cities in the weeks ahead, and often involve running up and down escalators and a good deal of shouting, flirting and singing of Brazilian funk songs. For many participants, although they may come from relatively poor urban areas, the events are also opportunities to show off costly brand-name clothing. Others contend that the rolezinhos, while not explicitly political, nevertheless open the way for new methods of protest at malls.