Over the years, many Wells Fargo customers have tried to sue the bank over fake accounts, but their cases have run into an increasingly familiar roadblock: arbitration clauses.

When customers sign up for accounts at Wells Fargo -- and at most other banks -- they sign contracts that oblige them to resolve disputes with the bank in private arbitration rather than in court. Wells Fargo has successfully argued that applies even in cases where customers have accused the bank of opening fake accounts in their names.

The argument goes something like this: Although a customer obviously didn't sign a contract when a fake account was created for them, agreements they signed when opening genuine accounts nevertheless require them to take all disputes with the bank to arbitration. Judges have generally agreed.

You keep saying, 'The board, the board,' as if these are strangers you met in a dark alley.

Much of the fraudulent account activity at the heart of the Wells Fargo sales scandal was centered in the Los Angeles area, Wells Fargo Chairman John Stumpf confirmed during his appearance before the Senate Banking Committee today.

The banking giant’s employees created some 2 million fake accounts nationwide to meet aggressive sales goals.

After Sen. Jerry Moran (R-Kan.) asked Stumpf what was different about the Los Angeles market, Stumpf did not provide an answer but said Wells Fargo was analyzing the issue.

Lawmakers on both sides of the aisle are sharply criticizing Wells Fargo’s chief executive, but Sen. Elizabeth Warren (D-Mass.) stands out for her outrage.

“You should resign,” she told John Stumpf, becoming the first member of the Senate Banking Committee to call for him to step down.

“You should give back the money you took while this scam was going on, and you should be criminally investigated by the Department of Justice and the Securities and Exchange Commission,” she said.

This was a systemic problem that you benefited from enormously, that the bank benefited from enormously, and you are scapegoating the people at the very bottom.

Chief Executive John Stumpf said this morning that Wells Fargo should have spotted problems in its sales system, but added that the root of the problem was a small number of bank employees who “did not do the right thing.”

That echoes recent comments from Wells Fargo chief financial officer John Shrewsberry, who said the employees fired for creating fake accounts “weren’t the high performers.”

“It was really more at the lower end of the performance scale, where people apparently were making bad choices to hang on in their job,” Shrewsberry said at an investor conference in New York earlier this month.

You should resign. You should give back the money you took while this scam was going on and you should be criminally investigated by the Department of Justice and the Securities and Exchange Commission.

Wells Fargo & Co. Chief Executive John Stumpf said today he first learned of the bank’s improper sales tactics in 2013, but didn’t recall exactly.

Members of the Senate Banking Committee tried to pin him down at today’s hearing. When asked by Sen. Sherrod Brown (D-Ohio) if it was when the Los Angeles Times uncovered the practices in December 2013, Stumpf would only say that he learned “later in 2013.”

Senators expressed surprise that Stumpf was not aware even as the bank began firing about 1,000 employees a year for improper sales tactics in 2011.

You have done something that has never happened in the last 10 years: united the committee on a major topic. And not in a good way.

Multiple senators on the Banking Committee want to know whether Chairman and CEO John Stumpf believes Wells Fargo should rescind, or "claw back," some of the compensation owed to Carrie Tolstedt, the executive who ran the bank's consumer banking unit that oversaw many of the sales practices.

But Stumpf dodged their questions several times, saying he was "not an expert in compensation" and would leave questions about Tolstedt's pay to a committee on Wells Fargo's board.

Tolstedt announced her retirement in July after amassing salary, bonuses, stock, options and other compensation totaling $124.6 million in her career, Fortune reported, although others placed the figure in the mid-$90-million range.