This is a linkpost for http://waitbutwhy.com/2017/04/neuralink.html
The key ingredient for a MAD situation as far as I can think is some technology with a high destructiveness potential distributed among multiple agents who cannot trust each other. To reduce my whole argument to its cartoon outlines: serious brain augmentation seems about as good an idea as handing everyone their own nuclear arsenal.
I think there is a whole long discussion about whether individual or small numbers of brain augments can somehow hope to outsmart whole societies of brain augments that are all working together to improve their augmentations. And also discussions around how much smarter pure AIs would be compared to normal augments.