Moral considerations aside, the real causes of the mass famines under Mao and Stalin can be understood from a perspective of pure power and political strategy. From the point of view of a strong centralizing regime trying to solidify its power, the peasants are always the biggest problem.
Urban populations are easy to control for any regime that firmly holds the reins of the internal security forces: just take over the channels of food distribution, ration the food, and make obedience a precondition for eating. Along with a credible threat to meet any attempts at rioting with bayonets and live bullets, this is enough to ensure obedience of the urban dwellers. In contrast, peasants always have the option of withdrawing into an autarkic self-sufficient lifestyle, and they will do it if pressed hard by taxation and requisitioning. In addition, they are widely dispersed, making it hard for the security forces to coerce them effectively. And in an indecisive long standoff, the peasants will eventually win, since without buying or confiscating their food surplus, everyone else starves to death.
Both the Russian and the Chinese communists understood that nothing but the most extreme measures would suffice to break the resistance of the peasantry. When the peasants responded to confiscatory measures by withdrawing to subsistence agriculture, they knew they'd have to send the armed forces to confiscate their subsistence food and let them starve, and eventually force the survivors into state-run enterprises where they'd have no more capacity for autarky than the urban populations. (In the Russian case, this job was done very incompletely during the Revolution, which was followed by a decade of economic liberalization, after which the regime finally felt strong enough to finish the job.)
(Also, it's simply untenable to claim that this was due to some special brutality of Stalin and Mao. Here is a 1918 speech by Trotsky that discusses the issue in quite frank terms. Now of course, he's trying to present it as a struggle against the minority of rich "kulaks," not the poorer peasants, but as Zinoviev admitted a few years later, "We [the Bolsheviks] are fond of describing any peasant who has enough to eat as a kulak.")
[...] SIAI's Scary Idea goes way beyond the mere statement that there are risks as well as benefits associated with advanced AGI, and that AGI is a potential existential risk.
[...] Although an intense interest in rationalism is one of the hallmarks of the SIAI community, still I have not yet seen a clear logical argument for the Scary Idea laid out anywhere. (If I'm wrong, please send me the link, and I'll revise this post accordingly. Be aware that I've already at least skimmed everything Eliezer Yudkowsky has written on related topics.)
So if one wants a clear argument for the Scary Idea, one basically has to construct it oneself.
[...] If you put the above points all together, you come up with a heuristic argument for the Scary Idea. Roughly, the argument goes something like: If someone builds an advanced AGI without a provably Friendly architecture, probably it will have a hard takeoff, and then probably this will lead to a superhuman AGI system with an architecture drawn from the vast majority of mind-architectures that are not sufficiently harmonious with the complex, fragile human value system to make humans happy and keep humans around.
The line of argument makes sense, if you accept the premises.
But, I don't.
Ben Goertzel: The Singularity Institute's Scary Idea (and Why I Don't Buy It), October 29 2010. Thanks to XiXiDu for the pointer.