hi kaleido,
not so. tax payers are on the hook to prevent them going out of business.
that was the lesson of the recent crisis and why they are said to be too big to fail. the failure of lehmann demonstrated that there are massive systemic effects in letting a large bank go belly up. governments (and therefore taxpayers) cannot afford to let it happen.
if a bank is not exposed to the risk of failure, taking risks makes sense.