Last week, Google released a beta application that provides walking directions in major cities such as New York, San Francisco, and Minneapolis. It's another sign that the search giant is getting even more specific about "organizing the world's information," right down to the sidewalk in front of your house. If you want to walk from your apartment in the suburbs to a restaurant downtown, Google will show you the best route with turn-by-turn directions you can print out or follow on your smartphone.

In 2006, David Holtzman decided to do an experiment. Holtzman, a security consultant and former intelligence analyst, was working on a book about privacy, and he wanted to see how much he could find out about himself from sources available to any tenacious stalker. So he did background checks. He pulled his credit file. He looked at Amazon.com transactions and his credit-card and telephone bills. He got his DNA analyzed and kept a log of all the people he called and e-mailed, along with the Web sites he visited.

What do you think happens when you connect your computer to the Internet?

You don´t have to be a conspiracy theorist or a criminal to be uncomfortable with the fact that your online movements are frequently tracked and recorded. Maybe you don´t want commercial Web sites using your browsing habits to inform their marketing, or perhaps you want to post an opinion to an online forum without worrying that it could be traced back to you.