SEC laws protect investors in cash accounts by not allowing short selling of your shares by the brokerage. Brokerages put clients in margin accounts when opening an account, so they can lend your shares without your knowledge to short sellers. Brokerages earn a fee by doing this. Be a proactive investor by maintaining a cash account. Cash accounts differ from margin accounts in that you have to already have the funds available prior to investing. Margin accounts allow you to borrow at prescribed interest rate. Cash accounts are like debit cards and margin accounts are like credit cards and allow short selling.