Communism

It was a bad thing.
Not only because of the things REEEEvolution said. Child prostitution, bread lines (which came AFTER the fall), wars and a fall of life expectency, but I live in Western Europe and the dismantling of the Soviet Union also triggered the dismantling of social democracy and rise of both fascism and rainbow capitalism in my own country and I sometimes don't know which one to be more disgusted by.
Well fascism of course, but like religious people I consider their ideas to be so outdated that I'm often more amused and amazed by their stupidity and backwardness than I am frustrated by them during an age where China currently is undeniably the largest superpower in the world.