What scares me about AI is the omnipresence it can give small groups. Imagine that you are a government keen on preventing a particular argument from gaining traction in the media. AI gives you a tool that can listen for the argument becoming developed in chatrooms, forums, comment threads, etc. Once detected, AI also gives you a strategy to attack the credibility of the argument. Governments apparently do something similar to this today, although it seems like a much more manual process [1]. Society will continue to see benefits from developments in AI through software like Google' Search, Apple's Siri, Spam Detection, Network Security, just to name a few. Although certain uses of AI will only be available to small and elite groups, and the fear probably stems from the one-sidedness of this powerful technology.
[1] http://www.newyorker.com/tech/elements/world-cracks-internet