It has failed in every venue that implemented it, usually disastrously, and often in rivers and oceans of blood and skulls. Poverty and even starvation follow in its wake. We're talking about an atrocity on the level of the Bee Gees' version of Sgt. Pepper's Lonely Hearts Club Band.
Lee Harris looks at the question, and it's an interesting look that taps into socialism as a religion that justifies itself by faith alone, the role and importance of myth in human life, and the challenge facing capitalism and liberty in response.
UPDATE: On a related note, see also "Activism's Onanist Fantasy Ideology," which Harris' essay illuminates in a new light.