The strip and the comments remind me of an episode of The Office, "The Golden Ticket," in which Michael wants Dwight to take the fall for the disastrous results of one of Michael's ill-conceived ideas. (Michael later wants to reclaim the credit for the idea when the ugly duckling turns into a swan later.)
I take PokerGrumpy's approach. Whenever a superior tasks me to do something, I send an email to him (or her) to document the conversation. I always include a line saying that a failure to reply is confirmation of the content. I also write emails to document conversations I have with known weasels who aren't PHBs.
@nelkins: I take a different approach. I follow up the conversation with an email describing what was requested of me and saying that I will start as soon as they confirm.
The beauty of my version is that it lacks the vague language they they would have used to give themselves an out in case of a failure. This technique is especially useful if what they want is something that is completely boneheaded that no sane person would ever request.
Isn't it fun watching them squirm while being nailed down? I know I have them when they follow up my email with another call to correct my email. After that I adjust my email and send it again for confirmation before I get started.