Objective observers mostly agree that it doesn’t make sense for banks to be in the securities business, not if they’re explicitly insured by the government. Wall Streeters invent rationalizations to support the current structure because a large chunk of their profits come from trading.

It’s very refreshing that John Reed, an architect of Citigroup — the biggest, most disastrous financial supermarket of them all — now says the merger was a mistake and banks should be broken up.

From Bob Ivry, Bloomberg:

Congress’ overhaul of U.S. financial regulations should include ordering banks to hold more capital, ensuring executives’ compensation is aligned with long-term profitability and banning firms that take deposits from also engaging in equities and fixed-income trading, Reed said.

“I would compartmentalize the industry for the same reason you compartmentalize ships,” Reed said in the interview in his office on Park Avenue in New York. “If you have a leak, the leak doesn’t spread and sink the whole vessel. So generally speaking you’d have consumer banking separate from trading bonds and equity.”

Lawmakers were wrong to repeal the Depression-era Glass- Steagall Act in 1999, Reed said. At the time, he supported overturn of the law, which required the separation of institutions that engaged in traditional customer banking services from those involved in capital markets.

“We learn from our mistakes,” said Reed, who wrote an Oct. 21 letter to the editor of the New York Times endorsing a division of banking activities. “When you’re running a company, you do what you think is right for the stockholders. Right now I’m looking at this as a citizen.”

Again, this is just half the battle. Getting dangerous activities outside of insured banks doesn’t mean the activities themselves, which in many cases still pose systemic risks, won’t continue to benefit from an implicit government guarantee.

As long as investment banks remain highly complex, systemically dangerous institutions, they’ll always have a government lifeline. (“No more Lehmans!”)