The cover story for the January 2009 issue of Popular Mechanics magazine is a piece I wrote about ways marketers, or even stalkers, can track people through technologies many of us use every day. Here’s a snippet from that piece: “Free Web services aren’t free,” says Gregory Conti, a computer science professor at the United States Military Academy at West Point. “We pay for them with micropayments of personal information. Users aren’t entirely oblivious to the fact that information is being collected, and they’re doing a cost-benefit analysis, but they’re not thinking long-term.” Even those who take the time to read a Web site’s privacy policy may not realize how many companies have access to their data. That’s because most Web sites pull advertisements, snippets of code and other content from a number of third-party sources, any one of which may track the visitor and use the data in a