The proliferation of networked mobile devices that can capture and communicate various kinds of data provides an opportunity to design novel manachine sensing environments of which this paper considers participatory sensing. To achieve energy efficiency and reduce data redundancy, we propose Aquiba protocol that exploits opportunistic collaboration of pedestrians. Sensing activity is reduced according to the number of available pedestrians in nearby area. The paper investigates the benefit of opportunistic collaboration in large-scale scenarios through simulation studies. To take microscopic interaction of social crowds into consideration, we adapt the social force model and include it as one of three mobility models applied in our studies. Though the simulation results depend on mobility models, they validate the benefit of opportunistic collaboration employed by Aquiba protocol.