Heard management guru Gary Hamel talk about the US banks today. And he was savage.

Forget all this talk about commodity prices and the US dollar. The name of the game is the US housing crisis and the banks that delivered it.

We were reminded of this with JP Morgan Chase writing off $1.5 billion in junk loans and Wachovia announcing it will slash jobs and find another $500 million to pay its legal bills.

Add to that UBS announcing that it will try and untangle its investment banking, asset management and private banking arms after writing down $43 billion. Now there will be speculation that this is the first step towards the break up of the group but realistically, that decision won't be made until the new board settles in.

The Houston Chronicle's Loren Steffy compares it all to a Shakespearean drama and reminds us that the Securities and Exchange Commission is doing zip to fix the problem.

Hamel says it's all so familiar, coming about through a combination of several forces: easy money (which often leads to a lack of discipline), securitization which allowed the banks to extend loans to people who should never have been allowed near the money, leverage, the complexity of various products like collateralized debt obligations, fraud, hubris and those two ever-present cheer leaders of human folly, greed and stupidity.

"One thing that came out of all this is that bankers are as susceptible to mania as teenage Japanese girls,'' Hamel said. "They really lost a lot of basic clear thinking in this process."

And the lessons are pretty simple: things that can't go on forever, usually don't, deviations from the mean are always temporary, returns and risk are correlated and stupidity really is contagious.

And the patterns, he says, keep repeating themselves. Bankers' stupidity will not go away.

"If you look at what's happened to banking over the last 20 years, about every seven or eight yeras, bankers all hold hands together and they jump off a cliff. It's kind of a bankers' bulimia."