This is a great TED talk about the 3rd replicators that are almost upon us. It will really make you think.
Science fiction has spent a lot of time on the idea of robots taking over after becoming artificially intelligent. Terminator, the Matrix, etc. But they always make the robots out to be another race who competes with humans. The reality is that they in no way need us once they can replicate themselves. They won't need to be malevolent, greedy or evil. They just need to be able to reproduce. And if they do so at our expense, or at the expense of the planet and its resources, we are screwed. The fragility of it never really occurred to me.