Twice now I have heard that communism failed because those tasked to run things had "imperfect knowledge". For example, the head of a hungarian shoe factory when it was a communist country, would make only one size of shoe all year. If you did not wear size 11, for example, you would have to buy a shoe that didn't fit or go shoeless.This has been explained to me by (by a local communist) as a failure due to imperfect knowledge. He claims, now we have perfect knowledge and if we try communism again we will have a perfect, sustainable system...