There is a great, old Russian joke that captures perfectly the essence of this emotion. It comes in the form of the "Peasant's Prayer:"

"Dear God, my neighbor Ivan has a pig, and I have none. Please God, kill my neighbor's pig."

Schadenfreude is a secret, guilty pleasure. It's reserved for those shut-the-office-door moments, those alone-in-the-restroom-looking-in-the-mirror moments, and those driving-home-in-the-dark moments when you can break out in a big, fat grin over the fact that that asshole in marketing finally got canned. Unlike its close cousin revenge, Schadenfreude is a dish best served piping, steaming hot -- but nibble it carefully, and always in a (very) private booth.