If someone were to ask me what I've been working on these days, I would not tell him or her that I'm writing a story. I would say, "I'm writing a short story," which means I'm working on a concrete thing, a literary commodity: I'm a serious writer. And you get all of this by adding the word "short" before it.
It's interesting how adding the word "short" to the word "story" gives it a certain amount of validity and stature that adding "short" to other words (like "man" or "bus") does not. (And it's probably worth mentioning how arbitrary such a description is, for I've read some short stories that are no more than forty words--and others that are longer than forty pages.)
But if that same someone were to ask me how I would describe myself, I would simply say that I'm a man. I wouldn't feel compelled to say that I'm a short man; the word short in this context doesn't lend the same sense of stature and seriousness that it does to the word story. This is something I hope changes under the presidency of Dennis Kucinich. Wait, what's that? He dropped out of the race...Well. That was a short campaign. [Rim shot!]
But seriously folks, there are other ways the word has come to defy its original meaning. Take, for example, the word "shorty" (often spelled "shawty") which can often refer to someone who's taller than you, and which is used in the title of the best song of the 1990s and, more recently, in the name of the worst rapper of the past decade. (What is "acapello," some kind of sparkling wine?)