Sandy Weill came right out and said it. If a bank is so large that if it fails it takes down the whole economy. That is, if a bank is too big to fail, it is too big He also said that investment banking should be separate from traditional banking, as it was under the 1932 Glass-Steagall Act.
He should know, he has had quite a career.
An excerpt from Wikipedia
Weill, shortly after graduating from Cornell University, got his first job on Wall Street in 1955 – as a runner for Bear Stearns. In 1956, Weill became a licensed broker at Bear Stearns. Rather than making phone calls or personal visits to solicit clients, Weill found he was far more comfortable sitting at his desk, poring through companies' financial statements and disclosures made to the U.S. Securities and Exchange Commission. For weeks his only client was his mother, Etta, until Joan persuaded an ex-boyfriend to open a brokerage account.
Building Shearson (1960-1981)
While working at Bear Stearns, Weill was a neighbor of Arthur L. Carter who was working at Lehman Brothers. Together with Roger Berlind and Peter Potoma they would form Carter, Berlind, Potoma & Weill in May 1960. In 1962 the firm became Carter, Berlind & Weill after the New York Stock Exchange brought disciplinary proceedings against Potoma.
In 1968, with the departure of Arthur Carter, the firm was renamed Cogan, Berlind, Weill & Levitt (Marshall Cogan, Arthur Levitt), or CBWL jokingly referred to on Wall Street as "Corned Beef With Lettuce". Weill served as the firm's Chairman from 1965 to 1984, a period in which it completed over 15 acquisitions to become the country’s second largest securities brokerage firm. The company became CBWL-Hayden, Stone, Inc. in 1970; Hayden Stone, Inc. in 1972; Shearson Hayden Stone in 1974, when it merged withShearson Hammill & Co.; and Shearson Loeb Rhoades in 1979, when it merged with Loeb, Rhoades, Hornblower & Co.
With capital totaling $250 million, Shearson Loeb Rhoades trailed only Merrill Lynch as the securities brokerage industry's largest firm.
American Express (1981-1985)
In 1981, Weill sold Shearson Loeb Rhoades to American Express for about $930 million in stock. (Sources differ on the precise figure.) In 1982, he founded the National Academy Foundation with the Academy of Finance to educate students that would graduate from High School. Weill began serving as president of American Express Co. in 1983 and as chairman and CEO of American Express's insurance subsidiary, Fireman's Fund Insurance Company, in 1984. Weill was succeeded by his protégé, Peter A. Cohen, who became the youngest head of a Wall Street firm. While at American Express, Weill began grooming his newest protégé, Jamie Dimon, the future CEO of JPMorgan Chase.
Before Citigroup (1986-1998)
Increasing tensions between Weill and the chairman of American Express, James D. Robinson III, led Weill to resign in August 1985 at age 52.
After a failed attempt to become the CEO of BankAmerica Corp. (and "take over" Merrill Lynch, according to a Jamie Dimon interview in 2002), he set his sights a little lower and persuaded Minneapolis-based Control Data Corporation to spin off a troubled subsidiary,Commercial Credit, a consumer finance company. In 1986, with $7 million of his own money invested in the company, Weill took over as CEO of Commercial Credit. After a round of deep layoffs and reorganization, the company completed a successful IPO.
In 1987 he acquired Gulf Insurance. The next year, he paid $1.5 billion for Primerica, the parent company of Smith Barney and the A. L. Williams insurance company. In 1989 he acquired Drexel Burnham Lambert's retail brokerage outlets. In 1992, he paid $722 million to buy a 27 percent share of Travelers Insurance, which had gotten into trouble because of bad real estate investments.
In 1993 he reacquired his old Shearson brokerage (now Shearson Lehman) from American Express for $1.2 billion. By the end of the year, he had completely taken over Travelers Corp in a $4 billion stock deal and officially began calling his corporation Travelers GroupInc. In 1996 he added to his holdings, at a cost of $4 billion, the property and casualtyoperations of Aetna Life & Casualty. In September 1997 Weill acquired Salomon Inc., the parent company of Salomon Brothers Inc. for over $9 billion in stock.
In April 1998, Travelers Group announced an agreement to undertake the $76 billion merger between Travelers and Citicorp, and the merger was completed on October 8, 1998. The possibility remained that the merger would run into problems connected with federal law. Ever since the Glass–Steagall Act, banking and insurance businesses had been kept separate. Weill and John S. Reed bet that Congress would soon pass legislationoverturning those regulations, which Weill, Reed and a number of businesspeople considered not in their interest.
To speed up the process, they recruited ex-President Gerald Ford (Republican) to the Board of Directors and Robert Rubin (Secretary of Treasury during Democratic Clinton Administration) whom Weill was close to. With both Democrats and Republican on their side, the law was taken down in less than 2 years. Many European countries, for instance, had already torn down the firewall between banking and insurance. During a two-to-five-year grace period allowed by law, Citigroup could conduct business in its merged form; should that period have elapsed without a change in the law, Citigroup would have had to spin off its insurance businesses. Weill's office holds a wood etching of him engraved with the words "The Shatterer of Glass–Steagall". Weill denies that the repeal of Glass–Steagall played a role in the recent financial crisis.
In 2001, Weill became a Class A director of the Federal Reserve Bank of New York. Class A directors are those elected by Federal Reserve member banks.
In 2002 the company was hit by the wave of Wall Street managerial restructuring that followed the stock market downturn of 2002.Charles Prince replaced Weill as the CEO of Citigroup on October 1, 2003.
In 2003 Citigroup repurchased $300 million worth of shares from Weill. It was reported among the $1.967 billion of "treasury stock acquired" in the Citigroup consolidated statement of changes in stockholders' equity. The average price Weill received for his shares was $47.14.
Advocate for bank break-up
On July 25, 2012 Weill apparently reversed course on the financial supermarket and stated “What we should probably do is go and split up investment banking from banking, have banks be deposit takers, have banks make commercial loans and real estate loans, have banks do something that’s not going to risk the taxpayer dollars, that’s not too big to fail,” Weill said on CNBC. “If they want to hedge what they’re doing with their investments, let them do it in a way that’s going to be mark-to-market so they’re never going to be hit.” 
To me, this should be big news. The guy who got rid of Glass-Steagall now thinks we need it. Its been a week and this story has gotten very little press.