Is it time to buy Goldman Sachs?

????Naturally, the big banks have opposed efforts to clamp down on some of their most profitable businesses, and it is far from clear that Lincoln's approach will become law.

????But it hasn't escaped notice that sucker bets at the derivatives casino helped bring down AIG (AIG, Fortune 500) and played a role in the civil fraud suit the Securities and Exchange Commission brought last week against Goldman Sachs.

????"At the heart of financial regulatory reform is reforming the over-the-counter derivatives market," Lincoln told the Senate Committee on Agriculture, Nutrition and Forestry Wednesday. "We must bring transparency and accountability to these markets."

????Derivatives aren't the banks' only Achilles' heel on financial reform. Dallas Fed President Richard Fisher, a longtime critic of the so-called too-big-to-fail doctrine, called last week for "an international accord to break up these institutions into ones of more manageable size-more manageable for both the executives of these institutions and their regulatory supervisors."

????Fisher cited a study by Bank of England financial stability watchdog Andrew Haldane disputing the supposed economic benefits of giant banks. Fisher and Haldane both noted that the cost of the government's implicit support of the biggest institutions runs well into the billions of dollars annually.

????Among other things, access to cheap funds enables the giant banks to grow at the expense of smaller, nimbler, more community-focused lenders, which would be more apt to lend to small businesses than devise new ways to separate clients from their money.

????In this view, the giant trading books that are now fueling big bank profits also help to make managing or regulating the giant banks essentially impossible.

????"When Lehman Brothers failed, it had almost one million open derivatives contracts - the financial equivalent of Facebook friends," Haldane wrote. "Whatever the technology budget, it is questionable whether any man's mind or memory could cope with such complexity."

????Just as it's questionable whether big profits at the big banks are worth celebrating.