These are boom times for complacency. To gauge just how comfortable the world of debt has gotten, consider:

• Bond buyers handed $2 billion last month to Ecuador, whose socialist president forced a default during the financial crisis while calling creditors "true monsters."
• So many investors piled into a May bond sale by Clear Channel Communications Inc. that the radio broadcaster, with a credit rating that implies default is almost a certainty, more than doubled the offering to $850 million.
• China's Logan Property Holdings Co. defied predictions of a slowdown in the nation's real estate market by selling $300 million of bonds in May. The developer has negative cash flow and total debt almost twice its cash and cash equivalents.
• Hellenic Petroleum SA in Greece, where the government has needed two bailouts in the past four years, borrowed the equivalent of $444 million last month. Lenders were so enthusiastic that they put in orders exceeding $1.37 billion.
• Florida's Orange County Industrial Development Authority issued $64 million of unrated debt last month to fund facilities near Orlando that convert sewage into fertilizer.

"It definitely feels like investors are getting overexuberant, and you can stay in overexuberant conditions for a while," said Fred H. Senft Jr., director of fixed income and equity research for Key Private Bank in Cleveland. "But when it turns, it will turn quickly and it will turn very ugly."

Halfway through a sixth year of near-zero interest rates by the Federal Reserve and unprecedented central-bank stimulus from Brussels to Tokyo, almost any borrower is able to raise debt with few questions asked, even as the World Bank cuts its outlook for global economic growth.

The value of bonds in the Bank of America Merrill Lynch Global High Yield Index has soared to more than $2 trillion. It took 12 years for the gauge, started at the end of 1997, to get to $1 trillion and only four years to add another $1 trillion. More than $338 billion of the debt has been sold this year, putting 2014 on track to top last year's record $477 billion.