What's the story with sad smileys? It is indeed a strange concept (one may even say an oxymoron¹). Everybody knows that smileys should be happy - that's the entire concept behind smileys - they should smileys. Yet there are unhappy smileys. They are even quite common. This is the hub where they will get the respect that they deserve.

When should you use sad smileys? Obviously not when you are happy... Sad smileys are there for you when you need to communicate that you are sad, unhappy or, in extreme cases, to express grief.

Who invented the sad smileys? I do not really know. But one known origin of the sad smiley is the fictional character of Pierrot.

Who is Pierrot?

Pierrot is a stock character of mime and Commedia dell'Arte, a French variant of the Italian Pedrolino. His character is that of the sad clown, pining for love of Columbine, who inevitably breaks his heart and leaves him for Harlequin. He is usually depicted wearing a loose, white tunic. The noticeable feature of Pierrot's behaviour is his naïveté, he is seen as a fool, always the butt of pranks, yet nonetheless trusting. Pierrot is also portrayed as moonstruck, distant and oblivious to reality. (original text here, wikipedia)

¹Oxymoron - An oxymoron (plural oxymora (greek plural) or, more often, oxymorons)("sharply dull" in Greek) is a figure of speech that combines two normally contradictory terms. They appear in a range of contexts, from inadvertent errors such as extremely average, to deliberate puns like same difference, to literary oxymorons that have been carefully crafted to reveal a paradox. (original text here, wikipedia). Now one can easily understand why Sad Smiley is an Oxymoron.