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Kai Ryssdal: Not all that long ago credit-card companies were looking for reasons to give us credit. As we all know now, it didn't take much to get a shiny new piece of plastic in your wallet. But with credit-card defaults rising, those companies have started looking for reasons to take some of that credit away. To help them figure out how, banks are compiling thousands of bits of data, like what you buy, where you buy it, sometimes even the company you keep. As Marketplace's Stacey Vanek-Smith tell us, your credit card is watching you.

STACEY VANEK-SMITH: So, two guys walk into a bar, have a few drinks and split the bill on their credit cards. One guy's unemployed and in serious debt. The other has a job and pays all his bills on time. The joke is actually on both of them. Those drinks may have just cost them their credit.

Robert Manning is the author of "Credit Card Nation." He says the first problem the card company sees? Booze. Especially if you don't usually put margaritas on your Mastercard.

ROBERT MANNING: Alcohol might be a red flag that you're despondent because you're about ready to get laid off from your job.

And splitting a bill with the unemployed debtor makes the employed guy look bad to his card company. And that's just the beginning. Say Mr. Good Credit rewards himself with a rare trip to the spa?

MANNING: And get a massage, red flag.

His card company might think he's trying to relax because he's stressed about money. And what if he decides to go bargain hunting?

MANNING: Oh my gosh, maybe you're about to lose your job. You're starting to downscale to lower-cost stores.

So, if you start splurging, it looks bad, and if you start scrimping it looks bad. Welcome to the post-credit-crisis world of risk management. Where your card company watches everything you do and then tries to figure out how likely you are to pay your bills.

Analyzing that information is called data-profiling, and it's a $25 billion business. One of the biggest players is Equifax. Tom Madison works in the company's mortgage division. He says business is up 50 percent over last year.

TOM MADISON: The general direction that the financial industry is taking is towards a place where the data they use to render their conclusions about credit worthiness is the heart and soul of everything that they do.

Madison says banks want more data and more kinds of data than ever. Peter Harvey is the CEO of Intellidyn. It uses data profiling to help companies market their products.

PETER HARVEY: Twenty years ago, you could get age, income, home ownership. Today, you can get thousands of variables. Now it sounds ominous but think about the amount of transactions that are online today.

Harvey plugs all those bits of information into intricate models, which examine your past actions, figure out what makes you tick and then predict what you will do. He could look at our upstanding bill payer and figure out where he wants to spend his next vacation.

HARVEY: It's knowing that their next trip was going to be a river cruise in France. What type of boat, what type of amenities.

Harvey says banks are some of the most sophisticated data profilers around and, they're very secretive about it. Regulators have brought some things to light. The Federal Trade Commission recently filed a suit against CompuCredit, which marketed the Visa Aspire card. Reilly Dolan was on the litigation team.

REILLY DOLAN: Compucredit was reviewing how consumers used the credit card, and it would lower the available credit to consumers based on their transactional history.

Things that branded card-users as risky: going to a bar, a marriage counselor, getting tires re-treaded, buying something off of an infomercial. That's right: your 2 a.m. Snuggie breakdown could cost you your card. Which sounds pretty heavy-handed, I mean, sometimes a Snuggie is just a Snuggie, right? NYU economist Lawrence White.

LAWRENCE WHITE: For some individuals, it will not be an adequate representation of their true credit worthiness. That's unfortunately just the nature of the statistical exercise.

White says the banks would rather risk cutting the credit of our upstanding bill payer than having another default on their books.

So the next time two guys walk into a bar, they should probably think about walking to an ATM first.

I'm Stacey Vanek-Smith for Marketplace.