Here it is , the short version.....
Naked short selling..... selling stocks that you don't own to people you never intend to deliver them anything more than an IOU to and taking the money and running.
Thats why so many people lost what they thought were secure retirement and stock portfolio's. The stocks never actually existed, only an empty IOU. And this happened under the nose of the SEC and they ignored it. Thats why we "had " to bail out the guys that were "too big to fail", so the government could cover their own ass for being complicit in that event. Ooops.. our bad... you pay.