Put another way, a poor quality bank bond that no one wants because the bank is in trouble is suddenly high quality debt if the Fed is prepared to swap it for a Treasury bond.

FORBES: The Question Warren Buffett Can't Answer

For one thing, it is hard to know how much companies have in fact lengthened the maturity of their debts because the interest-rate swap market allows them to swap those fixed bond payments into cheaper floating debt, a popular strategy in the investment-grade market.

ECONOMIST: Better to feast on cookies than junk bonds