Essentially, it is a chain of debt obligations that is only as strong as its weakest link.

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During its evaulation of its debt, the chain will close some or almost all of its 3, 000 stores in the United States.

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With trillions of dollars in debt acting as a ball-and-chain for much of Europe, the U.S. and the rest of the developed world, must detoxify their balance sheets before hitting the ground running.

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There is also a hefty dose of debt financing in this chain.

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When the U.S. Treasury and Federal Reserve Board decided to guarantee bank debt and inject capital into our major banks, it started a chain reaction in several sectors of the bond market.

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The chain sprung to life in August 2005 after the sale of its Canadian unit took about a billion dollars of debt off its books and swept Canada head EricClausEric Claus into the chief executive role.

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There's a risk that drugstore chain Rite Aid, which accounted for 13% of McKesson's revenue last year, may default on its debt.

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