>>kbenso+(OP)
Spam is the extreme example. What about family or acquaintances who compulsively forward every garbage blog post they come across on whatever their political obsession is? What do you do when they don't respect multiple polite requests to take you off their CC: list? At some point you go, "the hell with seeming disengaged and just letting this trash pass without comment."
I'll happily forfeit my right to remain aloof and to give no signs of engagement if I get annoyed to the point where I'd prefer to go to war.