One could start a war with a group one thought was easy to defeat, but if the casualties mounted to a certain degree any sane leader would realize that depleting his country (and it's usually a he) of males was simply a bad idea. Groups always had to do the "is it worth the lives" calculus when deciding on whom to pick a fight with (or who to surrender to). Drones changes that entire equation. Since the drone operator does not put his or her (and expect more "her") life in direct risk for the goal, killing becomes easy and bullying other weaker people becomes far easier to do. Even if the enemy can shoot down the drone, it is a drone. Another one, possibly more advanced this time can and will replace it.
Think of that episode of Star Trek, TNG where Riker and crew are on a planet in which all the inhabitants have been killed off by military drones. Each time Riker and crew destroyed one another, more advanced one was created and sent after them. Are we not headed in that very direction? There is already much discussion about the automation of these drones in such a manner that they can pick and choose who and what to kill based on "algorythms" rather than "is this right/moral" or "can I look my wife and kids in the eye?" or other human constraints on wanton killing.
Now that the robot genie is out of the lantern it will not be put back in. The recent Counterpunch article on the expanded use of drones makes this clear:
During the four years from 2004 through 2007, the CIA carried out a total of only 12 drone strikes in Pakistan, all supposedly aimed at identifiable high-value targets of Al-Qaeda and its affiliates...
Under Panetta, the rate of drone strikes continued throughout 2009 at the same accelerated pace as in the second half of 2008. And in 2010 the number of strikes more than doubled from 53 in 2009 to 118...
During 2010, the CIA “drone war” in Pakistan killed as many as 1,000 people a year, compared with the roughly 2,000 a year officially estimated to have been killed by the SOF “night raids” in Afghanistan, according to a report in the Sep. 1 Washington Post.
Now consider the other aspect of the use of these drones...a lot of this is going on in a country in which we have not declared war. If there is no declaration of war, then all innocent people killed during these attacks are not "collateral damage" but are actually murder victims. Furthermore; these activities have shown that the idea of extra-judicial killing is simply non-existent now. If the president of the US declares that you are a terrorist (or Ghaddafi) he (or she at some point) can simply send in the drone and kill without so much as a peep from lawmakers or international bodies.
It is very clear that drone warfare has rapidly changed the face of international conflict, possibly more than suicide bombers have.