content: I think you've hit on the scariest part: AI would be so incredibly useful. We would be stupid not to develop technologies to make everything as efficient as possible. It makes logical sense to have a super-intelligent AI working on all of the problems you mentioned. The movie I Robot touches on this, but it makes the AI have a mandate to protect humans. The AI is "three laws compliant," a reference to Asimov. It decides the best way to protect humanity is to take over control. Good movie, would recommend.