The ads keep coming: Let your credit history slip and so, too, will your lifestyle. Once you're branded with a poor score, it's off to the bad job, the bad apartment, the bad insurance, the bad life. It is the scarlet letter of the information age. But the credit-rating mega-industry makes some big assumptions when it sells credit as an indicator of character. After all, what does poor credit really have to do with a person's ability to be a good worker or a safe driver? And given that credit can be so easily savaged by job loss, illness or divorce -- events we're all susceptible to -- what can it actually say about a person's propensity to steal or to lie? The answer, critics say, is nothing. The evidence is slim to none that credit history accurately predicts any behavior outside of borrowing. "The credit bureaus have basically said we've got this data and we should use it for more than just loans," says Birny Birnbaum, executive director of the Center for Economic Justice, a nonprofit consumer-advocacy group that opposes credit scoring. "They've pitched the product to every possible business, and now they pitch it to the consumers for protection." "It's hugely overused," he says. In the end, critics say, the practice unfairly punishes people who've hit hard times and broadly discriminates against minorities and the poor, whose scores tend to be lower. Consumers are left with little recourse other than to keep an eye on their credit reports, often by paying the same bureaus that are peddling the data (the reports are available once a year for free.) "The only thing people can do is complain to their representatives to change the laws to not allow it," says Wendy Harrison, an Arizona civil-rights lawyer who represents clients adversely affected by credit scoring. In the beginning, a good tool for lending Few people would argue that the use of credit scores for its original intent -- to assess risk in lending -- is not a good thing. It wasn't too long ago that bank officers decided whom to trust based merely on a file folder and an opinion. "The people giving loans wanted to give loans to people who looked like them," says Liz Pulliam Weston, a personal-finance columnist for MSN Money and the author of "Your Credit Score: How to Fix, Protect and Improve the 3-Digit Number That Shapes Your Financial Future." "We have progressed beyond that, thank God." More from MSN Money Your 5-minute guide to credit scores How to get a credit report for free Estimate your credit score Protect your credit in a downturn Credit bureau move creates 'secret' scores By contrast, the credit score predicts future behavior based on actual past behavior, which is considered a reliable model. It is blind to factors such as race, gender and marital status. As a result, more people can gain access to credit, while lenders are better able to price risk. As the credit bureaus consolidated into the big three (despite the title, they are all for-profit companies) and information management dropped in price, the bureaus started tailoring their credit data to outside industries and making sales calls. "Now it's becoming increasingly common because a credit report is becoming a cheap form of a background check," says Evan Hendricks, the publisher of the Privacy Times and the author of "Credit Scores & Credit Reports: How the System Really Works, What You Can Do." From the perspective of insurers, employers and others, "it's legal, it's not expensive to do it, so heck, the balance tips in favor of using it," Hendricks says. "Everything I see means it's going to become more and more used by more and more entities." Expect your credit to be checked It's unclear exactly how frequently companies rely on credit information, because they don't disclose the information, citing reasons related to competition. (While credit bureaus and private companies may see, and profit from, consumers' private information, they're not about to let consumers see theirs.) In general, though, credit histories are fast becoming standard for people to meet these necessities: Employment: In 2006, 42% of employers conducted credit histories as part of background checks for new employees, according to the Society for Human Resource Management. That's up from 35% in 2003 and 19% in 1996. Video on MSN Money Boost your credit score To take advantage of lower interest rates, you need to have great credit. Here are some tips for improving your score. Interest continues to grow, for a wide spectrum of jobs, says Susie Henson, a spokeswoman for Experian, one of the big three credit bureaus, along with TransUnion and Equifax. The credit bureaus defend their use of credit reports, saying they're a valuable fraud-prevention tool when used in conjunction with other information. Credit reports can verify past jobs and cities of residence. They show whether bills are paid on time and whether an applicant owes money. They can even reflect spending sprees. "This can be a way to really have a second check to ensure that that truly is the person that you talked to," Henson says. "It's not just about assessing financial health. . . . It's really to look at how somebody has been rooted in their environment." Employers also worry that a high debt load might make an employee likely to steal or accept bribes. Bankruptcy lawyer Carl Starrett frequently hears from members of the military, even at the enlisted level, who need to declare bankruptcy in order to begin improving their credit scores for their security clearance and, hence, their jobs. The same is true in several other licensed occupations.