Derived by comparing your credit history and payment behavior with thousands of other borrowers, the scores generally fall in the range of 500 to 850. The higher the number, the better. According to Fair Isaac Corporation, a person with a FICO score of 720 or more will pay significantly less in interest on a mortgage than someone whose score is below 560.

Your financial shadow
The mortgage industry has used credit scores for years to help speed up the lending process. They're also widely used for car loans and are the driving force behind online, "instant" credit card approval.

Plus, they've become standard in the insurance industry for setting rates for car insurance. Employers use them to screen applicants, particularly those for money-handling positions. Landlords access them for potential tenants to see who's most likely to pay their rent on time.

And, of course, since credit scores aren't a deep dark secret to be kept from consumers at all cost, just about everyone is offering consumers the chance to buy them.

With so many companies offering their own version of credit scores, it's no surprise that Fair Isaac Corporation has a "certified score." The idea is that consumers can go to the company's Web site, purchase a current, official FICO score and "use that as a bargaining lever with lenders to get lower rates," Watts says.

Assistant Professor Mark Oleson, director of the Office for Financial Success at the University of Missouri and a licensed marriage and family therapist says that while he's read about financial institutions and insurance companies using credit scores more often, there appears to be a lack of empirical evidence to back up the claims that they're accurate predictors of other kinds of behavior.

"You can make a rational justification, but I haven't seen much proof," he says.

Still, it makes sense to him to expand the use of credit scores to such areas as employment screening.

"It is uncommon to counsel individuals with financial problems who don't have other kinds of problems," he says. "You're more likely to miss days at work, be less productive on the job, as well as have marriage and other relationship problems if you are struggling financially. It makes sense that if you have a low credit score that you are more likely to have problems in other areas of life.

Employers looking to screen a large number of applicants could easily see a credit score as an effective way to narrow the field, Oleson says.

"If I'm looking to hire someone and 50 people look exactly the same on paper, I can filter through applications and see who has that extra baggage," he says. "It seems like money management is an easy way to filter people. There's this line drawn for people who do it well or don't do it at all."

The biggest problem, of course, is the elimination of the human side of the decision-making process, Oleson says. Two people side by side could have the same $5,000 in credit card debt. But one of them could have run up the bill on a Spring Break bender while the other is a single parent who got laid off and used credit cards to feed her child.

Customized credit scoring
One trend in the use of credit scores that consumers should pay attention to is the tendency of lending institutions to overlay their own underwriting criteria on top of the score. The result is that a score will mean different things to different lenders. A score of 680 might be seen as average to one lender, but as quite good to another. The bottom line: If you don't like what you're hearing from one lender or credit card, go shopping.

Of course, every system has its pluses and minuses. As Oleson notes, if you have good credit, the system makes things easier for you. If you have poor credit, it can be a barrier to getting a break.

Harvey Warren, co-founder of the Coalition for Economic and Social Research, says that while credit scoring is a better system than the "financial chaos" of having no predictive model, he has serious concerns about them.

The problem, he says, is that while mortgage applications still get a good deal of personal attention, many other credit issuers don't look at anything except the score before giving an approval, particularly since a lower score translates into a higher interest rate. He sees a correlation between their burgeoning use and the record-breaking levels of consumer debt.

"When a guy calls me and says he has $850,000 in credit card debt on 61 cards, does [the system] work?" he says. "Is it a good system? Bankruptcies are at an all-time high . . . Maybe the people who do the card issuing and marketing and checking aren't up to the task."

Leslie Hunt contributed to this story.

-- Updated: Oct. 17, 2005