More than one analyst has predicted that 2007 would begin to see some private equity firms collapse under the weight of the debt.

Half of the IPOs on the New York Stock Exhange, in fact, were private equity firms making exits, Thain noted. This meant that the private equity firms were in fact the "biggest customers" for public markets.

With rising interest rates, buyouts look less attractive. "The cycle will change eventually, " he told the New York Times.

Elsewhere at Davos panel discussions revolved around a cheerful report forecasting a "Decade of Risk" in which the globe will be beset by the possibilities of environmental catastrophes, terrorism, oil price shocks, a Chinese economic crash, globalisation, pandemics, fires, floods and plagues of frogs. The Global Risks 2007 report, prepared by Marsh & McLennan companies, Citigroup, Swiss Re and the Wharton School Risk Centre, says that the 23 core risks it identified have worsened over the last 12 months.

"Catastrophic natural disasters in recent years have demonstrated that our ability to confront emerging risks depends more on the choices we make before a disruption than the actions we take during a crisis, " said Marsh & McLennan CEO Mike Cherkasky. "Only a systematic planning approach will ensure that countries and companies are prepared for the risk environment we presently face."