"In recent years, a number of companies have been accused[by whom?] of using naked shorts in aggressive efforts to drive down share prices, sometimes with no intention of ever delivering the shares. These claims argue that, at least in theory, the practice allows an unlimited number of shares to be sold short. A Los Angeles Times editorial in July 2008 said that naked short selling "enables speculators to drive down a company's stock by offering an overwhelming number of shares for sale."
"But sometimes it’s not easy to find those shares to borrow. Sometimes the shares are controlled by investors who might have no interest in lending them out. Sometimes there’s such scarcity of borrowable shares that banks/brokers like Goldman have to pay a fee just to borrow the stock."
"These hard-to-borrow stocks, stocks that cost money to borrow, are called negative rebate stocks. In some cases, these negative rebate stocks cost so much just to borrow that a short-seller would need to see a real price drop of 35 percent in the stock just to break even. So how do you short a stock when you can’t find shares to borrow? Well, one solution is, you don’t even bother to borrow them. And then, when the trade is done, you don’t bother to deliver them. You just do the trade anyway without physically locating the stock."