"The process can be seductive: information collected by websites has benefits, too. Based on previous purchase and search queries, Amazon can recommend books for readers "just like you." But in the wrong hands, similar information collected by Web sites and discount card companies could be used by health insurance organizations to boost premiums or by employers trying to figure out how many sick days you'll be taking each year. It could even make or break your chances of landing that new job, Dr. Birnhack says. A health insurance provider doesn't need to see your medical records to understand the state of your family's health. It can learn just as much by looking at your grocery bill. "If you use a discount card at a supermarket, information on your purchases is added to a database. If you shop for halal or kosher products, your religion can be inferred, and the purchases of fatty or gluten-free foods can provide an indicator of your family's overall health." Federal legislation in the U.S. regulates for some 15 different kinds of specific data sets, such as health data and credit histories, but not for information collected by club and discount cards or by commercial Web sites. And it's more difficult to write a law to secure confidentiality in those areas, says Dr. Birnhack." - Steven Perez from Bookmarklet