Privacy advocates have been critical of behavioral targeting, which is already used by other Web sites such as Yahoo. However, on its blog, Google explains its new use of behavioral targeting not in terms of privacy, but as a way of "making ads more interesting." Speaking as someone who isn't a particularly big fan of advertising, I'd say the only way to make ads more interesting would be to have them tell the truth. But I'll leave that fantasy aside for now.
How does Google do the actual tracking of your interests? It collects information from your use of YouTube, and from its AdSense network. And it also tracks you when you visit sites of advertisers. Here, from a New York Times article, is the best description of how it works:
Google is collecting information from YouTube and the sites in its AdSense network those on which it sells both text and display ads. When you see an ad on one of those sites, Googles computers will read the page you are on and try to figure out what it is about so it can associate you with one or more categories on its list.Although Google is being criticized for behavioral targeting, it deserves plenty of kudos for the way in which it lets you opt out of that targeting, and the clear way in which it explains what it's doing. It's a model that other sites should emulate. In fact, the New York Times says that it may well become a Web-wide model, and may even halt potential government regulation:
Separately, Google is now adding "retargeting" to the AdSense network. The company will record when you visit the sites of certain advertisers, and you will be shown ads for that company on the pages of other sites that display ads sold by Google. For example, if you check the prices of roses on a flower site, you may see rose ads for a week. This concept was developed 10 years ago by DoubleClick, which Google bought last year.
Given Googles position as the No. 1 seller of online ads, its approach is likely to put pressure on other companies to follow suit. Online advertising industry groups said it might help quell calls for government regulation.First off, you can see what Google determines your interests to be, which in turn determines what ads Google shows you. Head to the Google Ad Preferences page. As you can see in the screenshot below, not only does it show you your interests, but it lets you change those interests. You can also opt out by clicking the Opt out button. And the site even shows you the cookie which stores your information.
You can also opt out by visiting this page, which includes a great deal of information about Google's advertising and privacy policies.
However, even when you do that, it's no guarantee that the cookie won't end up tracking you again. That's because the opt out function tells the cookie not to track you. So if you delete that cookie for any reason, the next time you go to Google, you'll get a new tracking cookie. However, Google has a browser plug-in that will keep you opted out permanently. Go here to get it for your browser.