Here are some impressive videos from the University of Pennsylvania robotics lab showing a swarm of tiny quad-rotor model helicopters flying in complex 3-D formations under computer control. They can also swoop through tight openings and work together in teams.

Now imagine this same technology using full scale, military grade machines with ultra-quiet fans, night vision cameras, and hi-tech weaponry. A real swarm of those would be pretty intimidating, wouldn't it? Great for surveillance and crowd control. A couple of them could buzz around to attract attention while another one quietly records every face that looks up.