My first thought was how can these things be weaponized. Depending on how much weight these things can lift, speed, battery life, miniaturization, AI etc these things could eventually render meat based infantry obsolete.
If a state can afford to cheaply mass produce 1000s (or millions?) of such drones armed with blades (like the manhacks in halflife2), or even explosives then they effectively have a form of cheap robotic infantry without having to develop difficult navigation and obstacle avoidance AI for walking or wheel based robots.
Question is for the price of 1 human grunt how many manhacks could be afforded? Given they can be stored for nothing (unlike meat soldiers) I imagine a lot. Defensively they could be scattered around an area to sit idle like landmines, the difference being that unlike landmines they can move in to attack a target. Or they could be used offensively by sending in swarms of them to attack bases at night. I don't see how current ground infantry would be able to survive in an environment swarming with these things. It would be hard enough to see them let alone hit them.
These kind of drones will also be a big problem for counter-terrorism. How is any leader going to be able to do any outdoors speech in the future when an assassin could just release a dozen kamikaze drones 2 miles away?
I can imagine there will soon be an international ban on development of such drones for warfare, because typically when there is a game-changing weapon that is cheap and dangerous the big states ban it. For example using cheap lasers to blind soldiers or pilots is banned, but you are perfectly allowed to blow them up with expensive missiles!