Sanford Weill is frequently credited — and often condemned — for the rise of megabanks deemed "too big to fail."

The former Citigroup chairman, a part-time resident of Sonoma, surprised people on both sides of the divide recently by saying those institutions ought to be broken up, with Main Street banking separated from Wall Street trading to prevent another costly taxpayer bailout.

Even the interviewers at CNBC seemed startled when Weill said, "What we should probably do is go and split up investment banking from banking, have banks be deposit takers, have banks make commercial and real estate loans, have banks do something that's not going to risk the taxpayer dollars, that's not too big to fail."

As you might expect, Weill's about-face fell flat on Wall Street, where bankers insist they don't need any more oversight. Unfortunately, it also got brushed off by ex-Sen. Chris Dodd and Rep. Barney Frank, the co-sponsors of the regulatory reform law adopted on the heels of a $700 billion bailout of Wall Street banks in 2008-09.

"Too simplistic," Dodd sniffed to Bloomberg Business Week. Frank says the Volcker rule — a provision of the reform law that limits the ability of banks to trade stocks for their own benefit — offers adequate protection for the taxpayers.

We're not convinced, and not only because the Volcker rule is getting watered down in the regulatory process.

Weill isn't the first financier to urge Congress to reconsider deregulation. But he brings a unique perspective to the debate, and Congress' banking committees should ask about his changing views.

They certainly listened to his forceful advocacy for repealing Glass-Steagall, the 1933 law that created deposit insurance and, to protect those assets from the uncertainties of the stock market, erected a wall between commercial banks and investments banks.

The wall came down in 1999, clearing the way for Weill to build Citibank into Citigroup, a financial conglomerate with commercial banking, investment banking and insurance under one roof.

He retired in 2006, two years before the epic financial crisis. The company he created needed a $45 billion bailout and, this year, it was one of four banks to fail the Federal Reserve's stress test, a measure of their ability to withstand another economic crisis.

In retirement, Weill is said to keep a close eye on his old company's fortunes. He also has established himself as a philanthropist in his new community, contributing money and using his business connections to help complete the Green Music Center at Sonoma State University. Those gifts, and an honorary degree, have been met with sharp criticism from people who see the repeal of Glass-Steagall as the first step toward a costly economic catastrophe that is still playing itself out.

Perhaps, Weill's critics can find common ground with him on revisiting deregulation. Restoring the wall between banking and brokerages won't be easy, but Weill brings an insider's credibility to the cause.