When you visit your favourite online shopping site, you can buy a new book or CD with a single click. Your pager and mobile phone let you stay in touch with the rest of the world from just about anywhere. Your e-mail inbox is filled with suggestions for new goods and services that appeal directly to your interests. All this technology gives you instant access to the world. Unfortunately, though, it also gives the world instant access to information about you -- and it takes almost superhuman efforts to keep nosy strangers from poking around in your personal affairs. Today, e-commerce and the practice of gathering customer data, or profiling, spark vociferous debates about personal privacy. If you're in the business of selling over the Web, your motives are almost certainly well-meaning. By knowing more about your customers' likes and dislikes, you can save them time and present them with buying opportunities they might not know about. Amazon.com is the pioneering leader in developing personalised online shopping techniques that depend on a rich flow of information from customers. By analysing prior purchases, for example, the site generates customised lists of recommended books, CDs and videos each time a customer returns. And Amazon.com's One-Click shopping feature boosts sales dramatically by allowing shoppers to skip the checkout line and use a saved address and credit card number instead. David Sobel, from the US Electronic Privacy Information Centre, says, "The incentives just aren't there for the industry to provide meaningful privacy rights to consumers. We think there is a role for the government to play in establishing some basic guidelines and ground rules so that users aren't dependant on the various privacy policies of every Web site they go to. There should be basic rules that apply from one site to the next, so users know what their rights are." The brick-and-mortar world uses similar profiling techniques to build databases filled with personal information. More and more food stores are tempting shoppers with cards that track their purchases in exchange for discounts or free goodies. But because the club membership form contains personal information about each shopper, it's ludicrously easy to build a detailed dossier based on your purchases. If you bought a home pregnancy-testing kit last year, and this year you buy a case of disposable diapers every week, then the grocer can make some logical assumptions about you. As long as only one company is keeping track of your activities, these databases may seem harmless. But the growth of the Internet has dramatically increased the amount of information in circulation, and market-driven companies are now sharing their databases. With the help of online advertising agencies and data-mining software, online retailers can track every click you make and match it with external databases -- putting together remarkably comprehensive profiles about you and your habits. Take me to the Surveillance 2 ZDNet News special.