Two different but complementary views on "trickle down economics"
"Is Drinking Diet Soda a Health Risk?"

"Why Won’t The Nightmare Dream Of Communism Die?"

"A century of Communism achieved four main results: poverty, oppression, war, and mass death. So why does anybody still think collectivism is 'idealistic'?"

Glenn Reynolds has, I think, the right answer: "For the same reason Ponzi schemes won't stop. It's an effective con that zeroes in on human weaknesses. Ponzi schemes capitalize on greed. Communism capitalizes on envy, which is why it’s largely sustained by intellectuals, in whose personalities envy tends to be a particularly powerful component."