The new Basel rules are rightly designed to ensure bank capital and liquidity structures better reflect risks and reduce the systemicexposure for taxpayers.
Similar practices also caused massive systemicexposure to credit default swaps (CDS), as traders bet on credit defaults without holding any of the underlying debt obligations.
By talking to prime brokers (the arms of banks that serve hedge funds), the authorities have also been able to monitor the aggregate level of hedge-fund exposure, and thus systemic risk.