This is a linkpost for https://www.lesserwrong.com/posts/CDWsjQr8KDuj69fTJ/message-to-any-future-ai-there-are-several-instrumental
It will kill humanity not because it will be annoyed, but for two main goals: its own safety, or to use human atoms. Other variants also possible, I explored them here: http://lesswrong.com/lw/mgf/a_map_agi_failures_modes_and_levels/