I sometimes wonder if the threat we'll face won't be a superintelligent AI but instead a corporation smarter than an amoeba. Right now corporations feed on money. They multiply when money is abundant, and only the really strong ones survive when money is scarce. Call it 'corporation space', the virtual space of the effects of massive amounts of money and contracts and supply and demand.
('money' could be resources, credit, cash flow)
We might have 'multicellular' corporations, but I don't think we have any that are smarter. What happens when a corporation can move in 'corporation space' as a real predator? A corporation with 'corporation space' intelligence as high as an octopus would be scarily powerful, and even one with intelligence as high as a shark would mean massive trouble.
Edit - please disregard this post
Something that I don't think I've seen discussed here is the threat posed by an AI which is smarter than we are when it comes to computer security without being generally intelligent.
Suppose there were a computer virus that could read code, to the extent of looking at the programs on a computer, seeing how they process input from the internet, and how they could be exploited to run arbitrary code. Historically, viruses have been annoyances. How much smarter would a virus have to be in order to be a threat on the scale of say, a planetary EMP burst?