When renowned physicist Stephen Hawking repeatedly warns us about the impending robot apocalypse, we should probably pay attention. "The development of full artificial intelligence could spell the end of the human race," Hawking told the BBC yesterday. While he admits early forms of AI have been useful (it's clearly been a huge help for his speech systems), he worries that we won't be able to keep up with super-intelligent versions that outwit humans. Hawking made similar comments back in May when he called the development of full AI "potentially our greatest mistake in history." (Or maybe he just really hated Transcendence.) And he's not the only genius singing this tune; Tesla's Elon Musk is also afraid of a Terminator scenario. While plenty of scientists have far more measured expectations for AI, Hawking's comments are worth noting. We really don't know what's ahead for intelligent machines, so perhaps we should proceed with caution.