From my feeling, the 681 trillion amount should include both market value and notional amounts.

Many financial derivatives with huge notional amounts do not have high market values, especially for Interest Rate swaps and Credit Default Swaps (CDS).

CDO and CMO have different trenches and their losses could be quite different. Many losses go to different pension funds and the effects could be felt in a long time.

US and Japan are totally different. US are good at education, military, resources and USD is an international reserve currency.

The world is not go to end although this deleveraging procedure could be painful.

Only personal opinions.