Cash rich US corporations are issuing bonds just to take advantage of extraordinarily low interest rates. Companies such as Microsoft and IBM, which sit on billions of dollars of cash, find that it makes sense to accumulate new debt just because rates are so low.
http://www.nytimes.com/2010/10/04/business/04borrow.html
An interesting quote from the above article:
"Corporations now sit atop a combined $1.6 trillion of cash, a figure equal to slightly more than 6 percent of their total assets. In the first quarter of this year it was 6.2 percent of assets, the highest level since 1964, when it was 6.4 percent."
Good economic news might deflate the bond market bubble:
http://www.usatoday.com/money/perfi/bonds/2010-10-05-bonds05_CV_N.htm
Nobel laureate Joseph Stiglitz highlights some of the international consequences of Fed's ultra loose monetary policy:
http://www.bloomberg.com/news/print/2010-10-06/stiglitz-says-fed-s-rates-causing-liquidity-flood-currency-misalignment.html