I guess flying would help with the terrain, but payload is still an issue, unless they use something extremely lethal (like plutonium) for the poison. Again, what's the worst thing that could happen like if somebody has a picture of a rat on their t-shirt?
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I am not a huge fan of the recent expanded use of military drones. This precision bombing makes water boarding look absolutely friendly, and has concealed or downplayed the expansion of fighting into other countries. The use of professional military instead of the draft (I was drafted in 1970), gives the public a degree of separation from the savagery and sacrifice of ballistic warfare and killing. The use of remote control drones to do the killing, adds yet another layer of separation between the public and the dirty business at hand. This should never be easy or painless.
Not that I have a good solution for the worlds problems, but everything has consequences and unintended effects. Micro-drones seem like assassination tools, while maybe that will spare the rest of the family that are being taken out now by full sized drone attacks.
JR