Big Four auditors almost never go to trial.

FORBES: A Legal Secret Weapon May Help Hold Deloitte US Firm Liable for ChinaCast Fraud

Critics of the big four argue that auditors are well paid for the risks that they run, and that legal pressures are the only way to keep their feet to the fire, ensuring high-quality work.

ECONOMIST: Auditing firms: Opening the books | The

The Securities and Exchange Commission is said to be considering relaxing rules that make it difficult for a company to switch auditors should one of the Big Four fail.

ECONOMIST: Auditing

Many companies already find it difficult to switch auditors because they use one or two rival Big Four firms, in addition to their auditor, for other work, such as valuation or advice on internal controls.

ECONOMIST: Auditing

Some are more dramatic: having auditors appointed by regulators, or stripping out audit firms from the multidisciplinary monsters the Big Four have become.

ECONOMIST: Auditor rotation