http://www.deepcapture.com/category/antisocialmedia-with-judd-bagley/This is how I explained it to my parents:
Covered (Legal) Shorting:
Three stockholders own one share each of Widget Inc. which is valued at $100. A shortseller named Shorty believes that Widget Inc. is going to go under. He has $100. He pays $2 to Stockholder A to borrow his share which he agrees to return in a week. Note that there are now 4 theoretical shares in existence: Stockholders B & C still have their shares, Stockholder A's portfolio still shows he owns his stock of Widget Inc. even though he's lent it to Shorty. And Shorty is going around Wall Street claiming that he has a share of Widget Inc. to sell. That's four people claiming ownership to three shares. This drives down the price of Widget Inc. a tiny bit for a brief moment but theoretically, so long as everyone isn't shorting, it should all even out. Stockholder B thinks Widget Inc is doing great. He wants another share of stock. Shorty sells Stockholder B "his" stock (Stockholder A's stock) for $100. Now Shorty has $198 and no stock, but by the end of the week he has to give the note back to Stockholder A. This is called "covering" your bet. Luckily, Shorty is correct. Widget Inc. slides to $10 a share. Stockholder C wants to get the hell out of Widget Inc.! So he sells his share to Shorty for $10, who returns the note to Stockholder A. Once Shorty returns the stock to Stockholder A, there are once again only 3 shares of stock in circulation (giving the stock a little bump in value.) In the end, Stockholder A has his share, plus the $2 from Shorty (from $100 in net worth to $12 in net worth. A loss of $88.) Stockholder B has two shares of Widget Inc. Stock (from $200 in net worth to $20. A loss of $180) Stockholder C has $10 in cash (from $100 in net worth to $10. A lost of $90.) Shorty has $198 (from $100 net worth to $198 net worth. A gain of $98 dollars.)
Mind you, the upwards loss for Shorty is unlimited. If Widget Inc. stock shot up to $1000 a share he would have had to cover his bet and left with a total loss of $902. This is all legal because it doesn't really disrupt the system, theoretically. Covered shorting is not embezzlement.
Naked (Illegal) Shorting:
But the market doesn't work with people meeting face to face or an open system where everyone knows who has what. All trades go through the DTCC (Depository Trust) which reportedly holds all the records of trades on computers, but its records are secretive. (The DTCC is also protected by machine-gunned guards and it's almost impossible to get inside.) Moreover, the transition to internet trading has changed another aspect of the system--there is so much volume and it all happens so fast that no one expects to ever receive the physical piece of stock. This is how naked shortselling operates. It is termed "naked" because the seller never intends to "cover" their bet.
Three stockholders own one share each of Widget Inc. which is valued at $100. A shortseller named Shorty believes that Widget Inc. is going to go under. He borrows Stockholder A's share and sells it to Stockholder B for $100. Now four shares exist in the system. Maybe he sends the actual note. But more likely he is a trader "known" to have a lot of money and can float on his credentials. He tells Stockholder B that he has another share to sell if he wants it. He sends an IOU. In fact, because of internet trading, all these IOUs act as stock now. No one ever expects to receive a piece of stock in the mail, just like domestic airline carriers no longer send paper tickets. It's a "paperless" society. Shorty sells another imaginary share to Stockholder B at $100. Now there are 6 shares in the system. In fact, Shorty sells 1000 IOUs. He makes $10,000 out of thin air. At the end of the week, he hands the piece of stock back to Stockholder A. He keeps "borrowing stock" for the sake of keeping up appearances. Most of the time he is just borrowing an IOU anyway. There are now 1000 "shares" of Widget Inc. floating around the market instead of 3. The value of a perfectly sound company is diluted. If naked shorters hit a company with a coordinated attack, say entire companies devoted to shorting, they can "bet" that a company will fail by making it fail through selling IOUs they don't have and diluting the stock. The shorters make billions. The companies fold.
Now, imagine how much power someone like Cramer would have if he hooked up with the WSJ and the Street and they raised the price of stocks just to short them. It'd be pretty crazy. Deep capture says there's not enough money in the world to pay out all the fake stock circulating.