MF Global Holdings Ltd.

MF Global's failure became a brokerage-accountability test because a proprietary sovereign-debt strategy, unstable short-term funding, escalating collateral demands and a failing sale process converged with a customer-protection system that did not keep the legal segregation boundary intact under pressure. The central lesson is not that every risky position used customer money, nor that every dollar initially described as missing stayed lost. It is that an institution carrying customer property must be able to prove, throughout an intraday liquidity crisis, which cash belongs to customers, which cash is the firm's residual interest, who authorized every movement, when a deficit first arose, and how regulators, exchanges and insolvency fiduciaries can act before uncertainty freezes lawful customer access.