"I am worried. Things could unravel."

My professor of International Trade, Finance, and Banking wrapped up class today with this statement about the current world financial crisis.

After laying out the magnitude of the numbers underpinning the present situation, he noted that he made the statement as a professional who has taught and published in the field for over 30 years.  

He estimated the total economic hit from subprime mortgages and derivatives (when the latter are priced at last) may "substantially exceed the gross national product of all the economies of the world" - something in the range of 60-80 thousand billion dollars.