Steven Gjerstad and Vernon Smith explain why the housing crash ruined the financial system but the dot-com collapse did not:
Why does one crash cause minimal damage to the financial system, so that the economy can pick itself up quickly, while another crash leaves a devastated financial sector in the wreckage? The hypothesis we propose is that a financial crisis that originates in consumer debt, especially consumer debt concentrated at the low end of the wealth and income distribution, can be transmitted quickly and forcefully into the financial system.
It appears that both the Great Depression and the current crisis had their origins in excessive consumer debt -- especially mortgage debt -- that was transmitted into the financial sector during a sharp downturn.
It appears that we're witnessing the second great consumer debt crash, the end of a massive consumption binge.
How can one crash that wipes out $10 trillion in assets cause no damage to the financial system and another that causes $3 trillion in losses devastate the financial system?
In the equities-market downturn early in this decade, declining assets were held by institutional and individual investors that either owned the assets outright, or held only a small fraction on margin, so losses were absorbed by their owners. In the current crisis, declining housing assets were often, in effect, purchased between 90% and 100% on margin.