Short-selling pops up a lot as a topic of discussion, usually when the  markets are distressed in some way. I finally decided to write down some of my  thoughts on the topic.
 Stated simply, my position is that short-selling (as opposed to selling to  liquidate a long position) is 100% immoral since you are acting counter to the  interests of the party that actually owns the shares that you are selling short,  although mostly legal. Naked short-selling is illegal in addition to being  immoral. A short sale is the sale of something that you do not own. You may be  able to "borrow" shares to sell them short, but that is usually somebody's  broker "loaning" shares of a customer who has a long position that is "held in  street name" without informing them of that "loan" or in any way  compensating for either the "value" of the "loan" of the stock or any of the  loss that results from the downwards pressure on price from the short  sale. This is all legal, but still 100% immoral, unless you have the moral  values of a Wall Street trader.
 I would be tempted to say that short-sellers have the moral values of a piece  of dog poop, but that would be an insult to dog poop. In my personal hierarchy  of moral values, short sellers and the brokerage firms that "enable" them have  moral values somewhere well below the moral values of al Qaeda. The only people  with worse moral values than short-sellers might be partners at Goldman Sachs  and pedophiles. [I have already decided that I will never be applying for work  at Goldman.]
 Sure, non-naked short-selling is still legal, but slavery and a lot of other  barbaric practices were also legal at some point, so being technically legal is  no justification of moral value. Contributing to the detriment and even  destruction of the economic value of a portion of the real economy (since each  short sale does place downwards pressure on the stock price and stock price is a  key factor in a company's ongoing ability to raise capital) is clearly immoral.  But, some people clearly place a high value of short-term "financial" profit  even if it comes at the expense of real economic "value."
 There is one exception on short-selling, "shorting against the box", which is  the short sale of shares that you in fact own is perfectly reasonable since you  do in fact have an economic interest in the financial instrument that you are  selling. I wouldn't say that it is 100% moral, but at least it is marginal.
 Shorting a stock when you own the bonds is borderline in many cases and  immoral in some cases. If you bought the bonds at face value, I would say that a  short sale is a reasonable form of "defense". But if you bought the bonds at a  steep discount to par (a "fire sale" price), then short-selling becomes  borderline predatory. At a steep enough discount, the bounds can become more  valuable if the company goes into bankruptcy, wipes out the stock equity, and  causes the company to fire employees and void a variety of contracts. "Inciting"  that prospect by pushing the stock price low enough that the company cannot  raise capital would constitute predatory behavior and be a solid indicator of  lack of moral values.
 And if you throw CDS into that mix, you are downright and outright "evil" and  that may in fact qualify you as a partner at Goldman Sachs.
 The only "natural" sellers are owners -- by definition. So, the only  "natural" position of a "natural" seller is that they are an owner. In other  words, it is "unnatural" to sell that which you do not own.
 How can any short-seller believe that selling that which you do not own can  be anything other than immoral?
 How can any short-seller believe that selling that which you do not own can  add productive value to the economy and society?
 Buying, owning, and holding stock finances the development of productive  capacity in the economy. That is generally considered a good thing.
 The additional downwards pressure of short selling during times of financial  and economic stress can also damage the ability of normal, average, everyday  retail investors with 401K accounts to withstand the dire fear-mongering  promoted by short-sellers. These innocent retail investors end up selling at the  worst time. Short-sellers add no productive value to their finances or their  lives. How much more immoral does an activity need to be before we acknowledge  that it is anti-economic, anti-social and plain old immoral? How can we consider  such harm to individuals as anything other than immoral?
 OTOH, in normal, healthy economic times any financial "games" (e.g.,  short-selling) are a tiny portion of market activity and can simply be ignored  with no great loss. But in times of stress, such activities can begin to be the  proverbial tail that wagged the dog, and it is at such times that harm is  starting to occur, so it is at that stage when dysfunctional activities that  might be marginally tolerated in good times need to be completely shut down.  And, they need to be shutdown before any damage occurs, not after, as the SEC  did last year when it temporarily banned short-sales of financial stocks. As the  old saying goes, it does no good to close the barn door after the horses are  gone.
 Right now, here we are in the early stages of an economic recovery when the  near-term outlook is uncertain. It is at such times that additional capital is  critically needed to boost economic activity back to something resembling  "normal". Short-selling at times such as this adds no positive contribution to  the ability of firms to raise capital.
 In short (ha-ha!), short-selling NEVER makes a positive contribution to the  economy or the lives of normal people. It interferes with the primary function  of a market, to mediate the flow of information between real economic buyers and  real economic sellers. Interfering with that flow of information could never  possibly be considered a good for society, an essential requirement for  morality.
 A short-seller may eventually "cover" their "short sale", technically known  as "buy to close" or "short covering", but as a general proposition that hardly  compensates society or the economy for any economic destruction of value that  may have occurred in the interim. Just because short sales eventually are  covered or closed in no way makes up for the interim period where non-owners are  interfering with the ability of a company to raise capital in the capital  markets. The harm has already been done.
 Putting it simply (again), short-selling is a form of predation and does not  add productive capacity to the economy or "value" to society. It may be  profitable, but financial profit by itself does not mean an improvement in the  productive capacity of the economy or an increase in "value" to society.
 Any number of purported "benefits" are repeatedly put forward, but no list of  excuses or purported "benefits", no matter how long or how artfully constructed,  can ever excuse immoral behavior.
 I have seen a number of arguments (and even formal academic papers) in favor  of short-selling over the years and some of them do superficially "sound good",  but superficial is not good enough. It is usually deep down in the assumptions  were the problems lie. A lot of cute and clever logic and reasoning means  nothing if the assumptions are bogus. Bogus assumption #1: "If used responsibly,  in moderation, and according to law..." Well, I guess that eliminates 99% of  short-selling.
 Oh, and I would add that buying "put" options on stock that you do not own is  100% equivalent (and just as immoral) as short-selling.
 Even "hedging" a long position with a short position is of very dubious  economic or social value. Once again, it hides or distorts the information flow  in the market.
 And for those in the financial markets who are "morally-challenged", I  would put forward the following simple test: simply imagine if your neighbor did  something equivalent in the real world (outside of Wall Street and "the  markets") - would you conclude that they are "a good person"? If a neighbor or  person who you do not know "borrowed" your car without your permission and  returned it badly damaged and killed or badly injured several pedestrians and  other motorists while driving your car (again, without your permission), would  you say that their behavior was consistent with being "a moral person"?
 It has been said that if you leave your securities with a broker you can ask  to have them delivered to you so no one can short them. True enough (I think),  but that simply is not true for retirement accounts. No such option is made  available to customers with retirement accounts, such as 401K and IRA Keogh  accounts or for mutual funds. I would also note that no broker that I have ever  heard of discloses the short-selling  aspect of keeping stock "in street  name." Sure, a lot of people may informally know that, but it isn't even  recorded in writing or in any official documents of brokerage firms on the  Internet.
 To repeat one point: Some forms of short-selling may be legal (currently),  but legality is never a moral justification. No amount of excuses can erase or  balance out the inherent immorality of selling something that you do not own  along with the negative economic and social consequences that can result  from that attempt to "make a fast buck".
 Anyone engaging in short-selling has no business referring to themselves as  an investor.
 -- Jack Krupansky