That's where the juggling algorithm comes into play.

(I'm guessing the answer cumulates in anti-drone drones, e.g. air superiority drones. Drone dogfights!)

Or simply stronger windows.

Or a person can use a grenade launcher

Simple. Have the drone hold on to them for long enough that they explode before the others have a chance to return it.

From PBS's Rise of the drones http://www.pbs.org/wgbh/nova/military/rise-of-the-drones.htm...

They profiled a new type of drone which is basically a human-controlled missile. Fly it right into a window!

I'm actually a bit curious why we haven't yet seen any reports of organized crime related hits using cheap drones and explosives.

I'd just make the drones the bomb. Instead of the bomb deploy-er. These things will only get cheaper to produce anyway.

Yep, that's the way it will evolve, I think. Let's say you can mass-produce a drone with anti-tank explosive for $5000. That's much cheaper than guided anti-tank missiles we have now. And they can be designed to only work for 10 minutes, so no good quality materials required.

Make 1000 of them ($5 000 000 is sth like 1 tank), put them in groups of 20 in 50 places where you suspect enemy will attack. Program them to wait with sensors on, when they detect enemy tanks they go up, land on tanks and explode. Tanks usually have much less armor on the top.

Little ones with a small amount of thermite could fly into the gun barrels of main battle tanks.

Presumably the drone is the "grenade" and so performs evasive tactics. Targetted EMP? Or simply has a "balloon" to make it physically unable to exit the window again (bonus that the balloon blocks out natural light inside and seals the explosion magnifying the effect inside, eg for flashbang).

Smart grenades?