• When in doubt, do a Google search on yourself to see what kind of information is buzzing around the Internet about you.

• All it takes is a phone number to gain access to a wealth of marketing information on you.

Disloyal cards

Companies have found a new lucrative source for income: consumer data. Customer loyalty cards, such as those used at grocery stores, keep track of what you buy in exchange for a discount on your products. That data is then recorded and sold under your phone number or address to marketing companies. Schwartz said customers must weigh the benefits against giving out information about themselves with customer loyalty cards.

Some companies keep track of things without people knowing it. Take the color laser printer, for example. According to officials within the printer industry, miniscule yellow dots printed on documents have been used for years to trace a document to its source. According to an official from Xerox, quoted in a national news article, the nearly invisible yellow dots contain the make and serial number of a specific printer. The official also said the practice is fairly common among the major computer printer manufacturers. In order to tell if the dots are present on a document, one can shine a blue LED light on the paper.

The new concern

The one emerging technology that has privacy advocates the most concerned, however, is called RFID, for radio frequency identification. Already, RFID tags have revolutionized the retail industry. Using a relatively cheap thread of metal that emits a weak radio frequency, stores can keep instant inventory on products and make it easier to catch shoplifters. The potential of this technology could allow any item to be kept track of anywhere.

Within the next year, it is expected that companies will begin offering home RFID security kits with which people can place antenna stickers on their valuables. Sensors plugged in to outlets will alert your PC if something is being stolen. Some programs also will alert you if you leave your house without your keys or wallet.

Leading the way among retailers using RFID tags is Wal-Mart, which has mandated its top 100 suppliers to be RFID-compliant by this month.

"They exist today. Every item that we have will be able to be identified," Schwartz said. "That raises a whole bunch of questions."