It's an interesting strategy. Normally you don't see nations doing something like that, even though everyone knows a bunch of them do it - it would be weird for the State department to do that after a drone strike. I am not sure if it will have the intended affect though - surely the people being targetted know they're being targetted when people around them start getting blown up - and they don't need to be told on twitter. In terms of world opinion, this might backfire? Hard to say.