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To Tell or Not to Tell?

If you want to find out about tomorrow's weather, you'll get a more specific forecast if you provide your zip code to the weather service. But an online vitamin vendor doesn't need to know your entire medical history to sell you some echinacea.

Here's our rundown of personal information you should share only when it's absolutely necessary (Stop), the information you can share discriminately (Caution), and the information you can feel comfortable about sharing with anyone (Go). The rule of thumb: When in doubt, leave it out.

 Stop Social Security number, bank-account personal identification number (PIN), mother's maiden name, medical information, legal history, specific financial information (tax history, savings, mortgage, and so on), travel plans, employment history, and information about friends and relatives, including their home and e-mail addresses and telephone numbers.

 Caution Telephone number, street address, date of birth, marital status, employer, education, e-mail address, shopping preferences (music, books, favorite brand names, and the like), credit card number, hobbies and interests, affiliations (club memberships, political associations), and Web sites you've visited.

 Go Zip code, age, salary range, opinion surveys, and occupation. (Note: This information is safe to provide only when not transmitted along with other, more specific personal information.)

For more information on Internet privacy, visit the following sites: Privacy Foundation, Electronic Privacy Information Center, and Privacy.Org.