The same technology companies that make it easy to find content that interests you online are making it easier for advertisers to show you customized ads.
"One of the things that have changed recently is the ability for anybody to do this," explained Steve Beaty, security engineer at the National Center for Atmospheric Research. "It becomes easier and easier for both individuals and businesses to create this information about me and then it becomes easier to give that information up."
In print or on television, ads are targeted to the best guess of who will see the content based on prior statistics like ratings or distribution. On the web, a single ad space can be filled with an infinite number of messages tailored to each individual visitor.
"Things that I Google for will show up on Facebook these days," said Beaty.
For example, on TheDenverChannel.com home page KMGH-TV Reporter Marshall Zelinger was shown an ad about shows in Las Vegas after he had done web searches for an upcoming trip to that city. Meanwhile, on anchor Anne Trujillo's computer, the same ad square was filled with messaging about purses she'd recently browsed online.
"The searches that you've made through the years are kept in a database at Google and so that it has suggestions for you and those suggestions tend to be pretty relevant," said Beaty.
The results of that data are a conclusion about who the user is and what they are interested in. For Zelinger, the results are very accurate. Google identifies him as a male between the ages of 25 and 34 who is interested in travel, football, Denver, fitness and running.
"Certainly it is the case that the profile coming back about all of us can be fairly accurate and then therein lies a concern," said Beaty.
Google makes it easy to see the demographic assumptions associated with your account, offering an "Ad Settings" page. Google is just one of the 99 companies participating in the Digital Advertising Alliance's self-regulatory program for online behavioral advertising.
The DAA's website offers a tool for opting out of some or all of the 99 companies' targeted ads. By completing and submitting the form, all of the opt-out selections are saved in a cookie -- a small web-related file -- to the user's hard drive.
Of course if you have set your browser to block cookies to prevent websites from tracking you, gathering data about your visits or keeping you logged in, this may be a problem.
Within Google's framework, users can opt out of interest-based ads served by that company, but that doesn't stop ads from appearing in the future. It just means that ads won't be tailored to fit your search history.
In lieu of opting out of interest-based ads, Google also allows users to block individual advertisers. The gateway to that option is a little icon of a lower case "i" in a circle that appears near the ad.
Both the DAA and Google explain that opting out of interest-based advertisements will not stop other types of ads and will not stop companies or websites from collecting information about internet behavior. That data could be used for research, analyzing which ads are served or other purposes.
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