Is Artificial Intelligence a risk to Humanity?

In the article he talks about how concern for Artificial Intelligence that might pose a threat to us is considered a 'flakey concern'.  It was not that long ago that scientists considered near earth asteroids rare, until we put eyes on the sky and realized now many near misses happen each year.  Then again, I think that if a machine was to become self aware one of the first things it would do would be to hide its awareness from its creators (humans) just for sheer self preservation.
Cambridge to study technology's risk to humans
Could computers become cleverer than humans and take over the world? Or is that just the stuff of science fiction? Philosophers and scientists at Britain's Cambridge University think the question...