ETrade Financial Corp. lost more than half its market value after the online brokerage forecast a decline in fourth-quarter earnings and a Citigroup Inc. analyst said the company may go bankrupt.

Bank Failure. If it wasn't for FDIC insurance there would currently be a run on etrade accounts, which would cause them to collapse. This panic would spread resulting in a massive economic catastrophy.

ETrade stock falls 58% after forecast - The Boston Globe