Darlene Salerno considers herself a loyal customer of the Express clothing chain, shelling out roughly $2,000 for its trendy outfits each year for the past decade. On a recent shopping trip, she bought a tank top, a button-down shirt and some khaki pants, but realized when she got home that she had similar items in her closet. So a few days later she took them back to the store. She presented the items, the receipt and waited for her money.

Instead, the saleswoman handed her a slip of paper that said "RETURN DECLINED" and told her to call the toll-free number at the bottom for more information. She phoned and was informed her account showed "excessive" returns.

As the holiday shopping season gets into full swing, a number of major retailers -- including KB Toys and Sports Authority, according to store personnel -- are rolling out electronic systems that weigh the number of returns and exchanges a person has made, the dollar value of the items, and the dates of the transactions to decide whether a consumer should be granted another. The systems are designed to catch shoplifters and those who "wardrobe," wearing clothes and then returning them for a full refund.

But Salerno, a receptionist at a Manhattan financial firm, said she falls under neither category. She returns things often because she buys things often. She said she feels she has done nothing wrong -- the clothes were never worn and the tags were still attached -- but that she was treated like a criminal.

"I'm embarrassed to go into the store," said Salerno, 26. "I love their clothes, but I'm afraid to shop there now."

As more and more personal information is collected into databases, computers have been handed increasing power to make decisions about our everyday lives. The technological systems aim to solve costly and important business problems, but the proliferation of these "electronic blacklists" has alarmed consumer and privacy advocacy groups who say many databases have incomplete, incorrect or misleading information.

"Technology has made it cheap to do all kinds of surveillance and watch over people and make sure they obey the rules. But when a system makes a mistake, what can you do?" said Richard Smith, an Internet security and privacy consultant.

The Fair Credit Reporting Act of 1970 gives consumers rights concerning information used to make decisions about credit, insurance, employment or other services. Other federal laws impose disclosure requirements on information collected by the medical establishment or the financial services industry. But increasingly, companies are creating databases not envisioned by such regulations, and there is debate about which laws, if any, apply.

Peggy Twohig, assistant director of the Division of Financial Practices of the Federal Trade Commission, which administers the Fair Credit Act, said whether a particular information system is covered by it "depends on the particular facts of each system, and can be a complex legal question."

Among the databases being created is one for landlords that purports to list renters who have been evicted. Others claim to identify "known" spammers. St. Louis-based Talx Corp., meanwhile, has compiled more than 100 million employee records that contain names of companies, dates of employment and job titles. More than 1,000 firms, including American Airlines, FedEx Corp., Hewlett-Packard Co., Kmart Corp., Marriott International Inc., Microsoft Corp. and PepsiCo Inc., make use of the service to speed along the screening process for potential new hires.

But workers worry that some companies, for instance, use the word "inactive" to refer to people who have left the company for any reason; other companies use "terminated," a word that some employees have argued has negative connotations. Perhaps the most common complaint is that job titles are incorrect. One woman, Shelli Isiminger of Dover, Del., said one of her former employers reported that she was a "supervisor" rather than a "call center manager," a big distinction in her industry and one she worries has cost her jobs.

"To have a discrepancy, to make it seem like I inflated my title, is a kiss of death," she said.

Mike Smith, vice president for marketing at Talx, said that the company tries to facilitate communication between employees and employers but that it considers itself an agent for the employers and that any changes to records must be made through them.

Another company, DoctorsKnowUs.com, created a database of people who have filed malpractice claims as a resource for doctors. John S. Jones, a radiologist from Kaufman, Tex., who spent seven years compiling the information for the site, said he took it offline after some patients complained that it was impossible to differentiate between those with legitimate claims and those with frivolous ones, and that all could be denied care by those using the list. Since then, however, Jones has received hundreds of e-mails and phone calls from doctors who want the site back online, and he said in an interview that he is considering resurrecting it.

"It was public information. . . . I was simply aggregating it," he said. "The site was mischaracterized as a blacklist."

A spokesman for Limited Brands Inc., which owns the Express stores, declined to answer questions about its computerized return authorization system. Mark R. Hilinski, a co-founder of the Return Exchange Inc., an Irvine, Calif.-based company that provides technology for the retail chain, said the computer denies returns to 1 to 2 percent of customers at most stores. He said even though the database is not subject to the requirements of the Fair Credit Act, his company provides consumers a free copy of their report when they ask and it gives them an opportunity to correct inaccurate data. He added that very few have disputed the information.

"The system is often highly reliable. We have a very fair system to make us aware of any discrepancies they think they found in their report," said Hilinski, senior vice president of sales and marketing.

He said the company's privacy policy prevents him from commenting on individual experiences. The company's criteria for judging returns varies from retailer to retailer and is not disclosed because it might inadvertently aid those who want to abuse the system. It's possible, the company said, that a return rejected one day could come in the next day and be approved.

Hilinski added that the company is not aggregating return data from multiple retailers but that there has been interest from clients who want to share return information with one another.

Return fraud has been a major drain on retailers' coffers. Richard Hollinger, a professor of criminology at the University of Florida in Gainesville, said retailers in 2003 lost nearly $30 billion, or 1.7 percent of sales, because of fraud and that roughly half of that may be related to bad returns. In recent years, scammers have used the Internet to launder the money -- people steal merchandise, return it for credit slips at stores, then turn those credit slips into cash by selling them at a discount on eBay or other online auction sites.

Retailers like the Limited are fighting back against such high-tech fraud with high-tech defenses. Sometime in the spring, consumers and Express workers say, the store began replacing the black placards denoting its return policy to note that it was using the Return Exchange service. The new signs advertise the "Express Guarantee" and say consumers have up to 60 days to return items. However, the company's return policy also notes that it uses an "industry wide" system to authorize returns and that "under certain circumstances we reserve the right to deny returns."

Some consumer and privacy rights advocates say they sympathize with retailers' desire to root out fraud but said they are worried that disclosure about the electronic tracking system has been inadequate. Jordana Beebe, a spokeswoman for the Privacy Rights Clearinghouse in San Diego, said consumers should be told exactly why their return is denied and warned before they hit that point.

Salerno said the report she got from the Return Exchange showed she had made six returns from June to August for a total of about $375 but that in at least four cases the transactions were exchanges and she actually ended up spending more money on other clothes. She said she contacted the company by phone and by mail to complain. In one letter, Salerno wrote that she felt the computerized system impinges on people's "freedom on how they should or not spend their money." She said she has not received a response.

Hollinger, who consults for the Limited, said that cases like Salerno's represent the "teeny tiny glitches" in the system that he feels will eventually be worked out. "Over the decades, retailers realized they were leaving the door wide open for fraud and a number of the major ones realized that . . . there has to be some technological solution to this," Hollinger said.

But for all the money and effort retailers have spent on this high-tech system, there appears to be a low-tech loophole, Salerno discovered. After giving up on trying to clear her record with the company, she enlisted the help of a friend, who was able to return the unwanted clothes without hassle.

KB Toys is among the national retailers rolling out electronic systems that decide whether a consumer should be granted a return, based on shopping history.Shoppers visit Dulles Town Center mall. Retailers say return fraud has been a major drain on their coffers.