When you buy on margin, you are buying w/ money borrowed from the brokerage and the value of the stocks in your margined accounts are collateral to that loan. Some brokerages consider they are "in fact" owners of that % of the value of shares in a margined account that equals what they have loaned. Thus, they in turn, loan them out for a fee and interest to others who wish to sell them. And as Linda Ellerby says "and so it goes." Buying shares in a "risky investment" on margin is just not smart, it is, in fact, gambling