I think a number of terrorists are going to be willing to figure out how to hook such a system up to a gun on a $300 RC quadrocopter. I hope it's a small number. It's going to be interesting.
We weren't talking about psychopaths. Everything is a threat in the hands of a psychopath. Give a psychopath a spoon and I'd still be worried.
Also the targeting issues are vastly simplified and they're very effective in swarms.