Unit 48
　　Internet Threatens Privacy
　　In the past, if a shop manager wanted to know you better, he had to rely on a good memory for detail. They cane out from behind the counter to give you personalized service, browsed the shelves with you and made recommendations. Sometimes their recommendations were made with uncanny accuracy, based on hints they picked up about who you are and what you might want.
　　They are old tricks for winning loyal customers. Now take those tricks, add massive computing power and multiply the effect by a million. That's what is happening these days on the World Wide Web. On the Web, businesses are making great effort to know you better than you may know yourself. It's called personalization. Many e-commerce firms are betting their future on it.
　　In this digital marketplace, the "shop manager" may actually be a machine. It searches in its memory of information about you, analyzes it and creates a clear portrait of what you are likely to buy and do in the future. Not all companies approach personalization in the same way. For some websites, the approach is direct: they ask you to take a survey about what you like, and then make offers that match your interests. Another way is through IP addresses, the electronic place from which you browse the Web. The addresses provide websites with an easy way to target a particular person or household.
　　Amazon.com and many other sites also compare individual's browsing and buying habits to those of thousand and millions of other consumers in their databases. Using a technique called collaborative filtering, they can find out your likely interests. This is based on what they know about what like-minded people buy or do. A clothing store, for instance, would make a very different recommendation to a customer who is 39, married, intent on looking young and willing to spend US$500 than it will to a recent college graduate.
　　But this new use of Internet begins to trouble some computer users. They worry that advertisers can track you without your knowledge, and that files about them might be put to ill use somehow, or shared with wrong people. Sometimes they just don't like being watched.