Katie Couric's Notebook: Goldman Sachs

An SEC investigation into possible fraud at Goldman Sachs has Wall Street on edge - but publicly, CEO Lloyd Blankfein is as cool as a cucumber - too big to flail.

He's insisting in a message to staffers that the focus is on one employee, presumably the young trader Fabrice Tourre, and bad investments in lousy mortgage loans cost Goldman a lot of money, too.

Financial experts say it is implausible - if not impossible - that just one person is responsible for duping investors.The Wall Street Journal reports that the SEC may widen the investigation...which probably has several financial institutions in a cold sweat right now.

Greed is definitely not good - but it really isn't illegal. Fraud is, and if a crime was committed the perpetrators will be punished.

But looking at the big picture, Wall Street may need a big cultural shift - a new way to incentivize people to do the right thing - because shame and bad publicity sure aren't stopping them.

That's a page from my notebook.

I'm Katie Couric, CBS News.