I think leverage made the difference - but at the same time, leverage ratios of European banks are significantly greater than that of US banks. There are others who have also said that it was the bubble in excess capital/credit which made the difference between this one and the tech / real estate bubbles of the past. This excess capital was caused by a number of factors that included the USD as a reserve currency (which is why those like Stiglitz now think that a move away from this is a good thing - though this is happening because of the massive borrowing by the current US Administration) and prolonged low interest rates by the Federal Reserve,