Financial advisers and consumer advocates say there are drawbacks to an all-cash existence beyond the nuisance and expense of running to the A.T.M. (A study this year by Tufts University, called “The Cost of Cash in the United States,” found that the average American spends 28 minutes each month, or 5.6 hours a year, traveling to banks or A.T.M.’s to get cash. It found that the average fee to use a non-network A.T.M. is now about $3.85 per transaction.)

For one thing, cash is not an option with online purchases. And vowing to use cash is a knee-jerk response that doesn’t necessarily make sense, some say. Adam Levin, chairman and co-founder of Credit.com and Identity Theft 911, which provides data protection and management services to businesses, said he told himself to use cash when he went to a Target shortly after Christmas. But the truth is, he said, “That is not realistic.”

“Cash has its own drawbacks in terms of possibly being mugged and of keeping track of your expenditures,” said Susan Grant, director of consumer protection at the Consumer Federation of America, an association of consumer organizations around the country. There is also the danger of losing it; Ms. McNamee noted that she has found loose bills in the laundry.

Besides, said Ms. Grant, “You don’t want to be carrying a bag of money into Best Buy to buy a flat-screen TV. People shouldn’t have to resort to that for peace of mind.”

Mr. Levin noted that it was important for people to build up a credit history. Still, he said: “People are right to be terrified about what’s going on with these breaches. I think we have to face facts, that breach unfortunately is the new normal. It’s the new black. It’s just where we’re going. We have to focus on monitoring and damage control.”

Rather than resorting to paying cash, it is more important for people to monitor their bank and card statements every day, he said, and to make sure never to use a debit card for an online purchase. “You’ve got to live your life,” he said, “but you’ve got to add one additional layer of vigilance.”

Already, some of the cash vows are proving to be about as temporary as those no-cupcake pledges. Kenyetta Kelley of Dothan, Ala., had her debit card information stolen after she used the card on Black Friday at Target. (She learned this when she tried to use it at another store soon after and it was declined.)