Eliezer claims that randomness is always bad; many other people claim that one way randomness is good is that it is unbiased. Partitioning subjects into experimental conditions must be unbiased.

This is perhaps a useful place to illustrate the "randomness hath no power" argument: randomness is unbiased in expectation but we actually expect the absolute amount of biasedness for a randomly selected assignment to be nonzero. When biasing factors are known ahead of time, we do better by controlling for it directly (with, say, a paired assignment).