Don’t look now, but video surveillance is hot. It was inevitable. The willing surrender of privacy and the fear of bad actors make a potent combination. Earlier this month, police in Dubai enlisted a new recruit. By the end of the year, a diminutive self-driving car will begin patrolling city streets. The robotic rig will feature cutting-edge video gear, networked facial-recognition software and an aerial drone, in case undesirables go off-road. Boosted by emerging technologies, video surveillance has become a service. And it is about to explode.