"We are aware of the credit quality of [WaMu's] portfolios and will manage risk appropriately."

Credit-card losses are already taking a bite out of lenders' balance sheets. Bank of America, the nation's second-largest issuer behind JPMorgan, revealed on Oct. 6 that roughly $3 billion of its $184 billion credit-card portfolio has soured, a 50% increase from a year ago.

At the same time the bank, which is also dealing with the broader financial tumult, said it would have to cut its dividend by 50% and raise $10 billion in fresh capital. The stock stumbled more than 25% the next day when investors largely scoffed at the new shares BofA was offering.

"The good news for us is that we have the strength to get through this, but the bad news is that the earnings recovery does take a while," says BofA spokesman Bob Stickler. "We are prudently adjusting our underwriting standards to adapt to changing economic conditions."

Likewise, American Express (AXP), which caters to wealthier borrowers, upped its provisions for credit-card losses from $810 million to $1.5 billion in the latest quarter, a sign that even upscale consumers are having trouble. "We have enhanced our credit models and continue to prudently manage our risk by scaling back some card acquisition efforts and reducing credit lines where appropriate," says an AmEx spokeswoman.

The industry's practices during the lending boom are coming back to haunt many credit-card lenders now. Cate Colombo, a former call center staffer at MBNA, the big issuer bought by Bank of America in 2005, says her job was to develop a rapport with credit-card customers and advise them to use more of their available credit

Colleagues would often gather around her chair when she was on the phone with a consumer and chant: "Sell, sell." "It was like Boiler Room," says Colombo, referring to the 2000 movie about unscrupulous stock brokers. "I knew that they would probably be in debt for the rest of their lives." Unless, of course they default. Responds BofA spokeswoman Betty Riess: "The allegations do not reflect our practices. The bank has nothing to gain by extending credit to people who do not have the ability to pay us back."

Now regulators and politicians are trying to curb some of the industry's abusive practices by limiting interest rate hikes, abolishing certain fees, and cracking down on questionable billing practices. Under rules proposed by the Federal Reserve, a borrower would have a 21-day grace period before being hit with a late fee, instead of the few days offered by some firms now.

A similar plan working its way through Congress would allow banks to increase rates only on consumers' future purchases—not existing balances. And under both proposals, credit-card companies would have to allocate account holders' payments equally to balances with different interest rates. Currently, firms first apply payments to the debt with the lowest rate, which means it takes longer and makes it costlier for consumers to pay off their debt.