One danger signal will be if the Chinese banks start using their idle domestic deposits to fund a lending bender abroad.

ECONOMIST: Japanese banks

"A high payout in the European telecom sector is nowadays more a danger signal that the dividend yield is not sustainable, " he adds.

WSJ: Investors Hang Up on Europe's Telecom Stocks

The danger signal for technology and financial services at the end of last year, for example, was that their weightings had each reached almost 20% of the market.

FORBES: Watch your sectors

This was not the only danger signal.

ECONOMIST: The Madoff affair

There are currently no severe flood warnings, which signal a danger to life.

BBC: Wet weather affects Britain's rail and roads

"Well intentioned efforts to reduce exposure to nuts actually fans the flames, since they signal to parents that nuts are a clear and present danger, " said Professor Christakis.

BBC: peanuts

The advent of new technologies like hit-to-kill missile seekers and advanced signal processors greatly increased the defensive potential of the system while reducing the danger of collateral damage.

FORBES: Missile Defense Becomes A Navy Mission

With my indicators on a sell signal for bonds since August 16, I have been warning about bonds being overbought and in danger of rolling over into a serious correction for several months.

FORBES: Who Will Buy All Those Treasury Bonds When The Fed Stops?