Amit Ghate defends speculators and short-sellers in this excellent OpEd from the Ayn Rand Institute. Here’s an excerpt:

…So just as doctors specialize in identifying and evaluating the facts affecting health and disease, speculators and short-sellers specialize in identifying and evaluating the facts pertinent to market prices. They make it their business to understand economic facts like supply and demand, and then risk their capital on their judgment, properly profiting if they’re right and losing if they’re wrong. Thus in a free market, rather than prices being set by wish or decree, they are set by a rational process, one which benefits from the knowledge of all who participate.

For instance, if speculators believe that future oil supplies won’t match demand, they buy oil, increasing its price. If they’re right, and oil prices continue to increase, they sell their positions, profiting from their insight but also capping prices as their supply comes to market; furthermore, their initial effect on prices signals to the market that greater oil supplies are needed and reduced oil consumption is appropriate — efficiently allowing market participants to adjust their actions to the facts.

So too for short-sellers. If they judge that Enron is cooking the books, or that Lehman is insolvent, they can seek to profit from their insight by short-sales. These lower stock prices in the present and convey to the market that there are potential problems with the companies, helping others avoid losses in the stocks. And if shorts are proved correct, rather than exacerbating any price slide, they actually mitigate price declines when they buy their positions back. (Of course, short-sellers, like speculators, only profit if their judgment is correct. If they short a productive, undervalued firm, say, e.g., Wal-Mart or Apple, they lose when the actual facts belie their predictions.)

…Speculators and short-sellers don’t create facts, they seek to identify and respond to them; and in the process they help adjust prices to economic conditions and establish smooth and liquid markets. As a result — instead of being scapegoated and banished–they should be respected and welcomed for the productive role they play in our markets.