If you’re like me, you probably have a half dozen or more of those little rewards cards dangling from your key ring. Mine are for the drug, grocery, book and sporting goods stores I visit the most often.

Recently Panera Bread did away with its stamped card for a free cup of coffee after purchasing so many in favor of one of those rewards cards. While the company didn’t ask for any of my personal information, most card issuers do.

By using these “membership” or “loyalty” cards, you receive discounted prices, points or cash back toward future purchases that you otherwise wouldn’t receive.

I am a member of the group that has provided my personal information multiple times. I look for my Extra Bucks at the bottom of my CVS receipt at the end of each quarter. And I have probably visited Panera Bread more since I received the card now that the store offers me a free pastry or coffee after so many lunches I buy.

When you load groceries into your cart, you're probably not worried about whether your supermarket chain is compiling a profile of you based on what you buy, and storing that information for its own use. After all, who cares if you buy one brand of laundry detergent over another, or prefer name-brand frozen dinners rather then store brands?

Supermarket chains care and so does your drugstore. While these discount cards offer you what seem like great bargains, stores are using them to keep tabs on what you purchase, how often you shop, and what your buying preferences are.

According to a 2004 poll conducted by Boston University's College of Communication, 86 percent of American shoppers use some form of store loyalty or discount card, and the majority of them say the benefits of the card are worth giving up some privacy.

While retailers maintain that they only analyze collective data, some critics have questioned whether it isn’t just a matter of time before records of individual consumer preferences are either sold to third parties or made available to investigatory agencies. In fact, some apparently isolated examples of that have already occurred.

For example, in a 2004 Washington state case, a suspected arsonist was arrested after police tracked down a fire-starter unit with a Safeway label attached. Safeway provided police with the suspect’s purchase history, revealing that he had bought a fire starter a month earlier. The charges were later dropped, but the point is that the store gave access to the customer’s personal information to authorities.

Are you willing to surrender some personal information about yourself to save money?