1. A method for use in a video surveillance system, the method comprising generating a plurality of hypotheses, each hypothesis comprising a respective different set of hypothesized trajectories of objects hypothesized to have been moving through an area under surveillance at a particular time, identifying at least one of said hypotheses as being more likely than others of said hypotheses to represent the actual trajectories of the actual objects moving through the area under surveillance at said particular time, and utilizing said at least said one of said hypotheses to determine whether at least one predefined alert condition has occurred within the area under surveillance.