I don't know if "Drone warfare" could be called questionable - it's just a different form of "Killing-at-a-distance". Armies of all nations have used Artillery near cities for over a CENTURY. That too, can fall and kill civilians in fire zones. Just because the artillery officer doesn't "see" where the shell lands doesn't make it any better or worse than a drone operator. Arguably, drones are better than what people have done before - bombing from the air, using artillery cannons, using blind rockets - all those things kill in just the same way and pose just the same risks to the people they are targeting.
You might be able to make a claim that TARGETING enemies in civilian areas is unethical. You could argue that the war in the Waziristan region of Pakistan is immoral (I don't think it is, but you can make that argument logically). But the idea that drone warfare is somehow "worse" than bombing using jet fighters or ground attack craft or good ol' fashioned artillery bombardment, is absurd. Getting hit by an artillery shell and getting hit by a predator drone hellfire missile messes you up in the same way (i.e explosive trauma and burns).
If you don't like the war in Afghanistan and you think the civilian casualties are unacceptable, then fine, you can make that argument and I'll respect your argument even if I somewhat disagree with it. But to portray drone warfare as some sort of super-evil thing that is totally the worst thing ever is just stupid. It's another form of "Killing-at-a-distance" - which began with the Cannon, then the Musket, then the Rifle, then the long-ranged-rifle, then the artillery shell, then the tank shell, then the bomber, then the laser-guided bomber, and now to the Drone.
Is killing with drones really worse than killing with, say, an A-10 warthog or an F-18 jet fighter dropping a bomb on a house? I don't think so. They're equally bad, but drones aren't "worse".