Then it's hard to tell where the line between (cyber) warfare and social engineering can be drawn.

Is what Facebook did[1] (does?) warfare? I sometimes like to dabble in hyperbolic alarmism, so I'm inclined to want to say yes.

Maybe it's a sign of progress that we now consider emotional manipulation "war". It's probably less harmful, by all accounts, than slaughtering each other.

1. https://www.theguardian.com/technology/2014/jun/29/facebook-...