But as happens in Wall Street all too often, what the wise do in the beginning, fools do in the end. In the last few years zero-coupon bonds (and their functional equivalent, pay-in-kind bonds, which distribute additional PIK bonds semi-annually as interest instead of paying cash) have been issued in enormous quantities by ever-junkier credits. To these issuers, zero (or PIK) bonds offer one overwhelming advantage: It is impossible to default on a promise to pay nothing.

