Imagine you are an enemy of a government that has “killer” versions of these things, you are at your compound and hear a slight whirring sound, look up, and see 10,000 of these little critters converging on you.
Don’t even get me started.
What if you take out one? Does it screw up the works?
Or- how about a more silent version on one that will target one individual? Like that assassin drone in Dune?