Sorry, but this post being moderated 5 completely discredits the competence slashdot's user base. I used to work in the financial institutions group (advising banks & insurers) of a major US Investment Bank for the last two years and witnessed the impact of the Lehman Brothers collapse on the financial system and especially other banks first hand.
The global financial systems are too interlinked that ANY significant bank would have survived the collapse of even Lehman Brothers without significant government intervention - and no being a prudent bank would NOT have helped!
Being prudent only impacts the asset side of the banks balance sheet i.e. a prudent bank will take less losses, however, this really doesn't help in staying solvent.
The business model of banks is very simple. They borrow money from
- other banks
- from customer deposits
- central banks (repo'ing assets)
add a charge (spread) on top of their funding costs (i.e. what they pay for the above) and lend it to out again. Sure, they can also trade themselves and do advisory business but borrowing and lending is really the core.
Quite simply, after the Lehman collapse banks weren't able to borrow money any more:
- investors were not willing to buy bank bonds any more
- banks stopped lending to each other
- customers withdraw money from their bank accounts
- Central banks tried to relax requirements to borrow money from them but this doesn't make up for the above (moreover, this already is government intervention)
This happens because investors & customers lost faith in the banking system and were afraid of another insolvency. Moreover it's a vicious circle, as soon as people are aware a bank has issues they withdraw their money making it even harder for the bank to survive.
As banks have to continuously refinance themselves (as bonds they issued mature etc), not being able to borrow money any more will let a bank that is perfectly fine on the asset side go belly up within days or weeks. I've seen it, post Lehman every other week a new (PRUDENT) bank almost went bankrupt and could only survive with government intervention.
You see being a prudent bank helps on the asset side and in the medium term on the liability side but in the short term after a major bank collapsed EVERY bank can go bankrupt within days given that they are extremely vulnerable on the liability side.