Here's one for the books, try covering 2m shares that DON'T EXIST....(SHHH the toxics are extinguished, but don't tell shorty)
An investor sells shorts associated with shares that they do not possess and have not confirmed their ability to possess. If the trade associated with the short needs to take place in order to fulfill the obligations of the position, the trade may fail to complete within the required clearing time because the seller does not actually have access to the share. The technique is seen as very high risk