Google and Facebook are some of the most prominent trackers, according to Ghostery.
Google is in the top ten of the most widely used trackers based on the various services the Internet giant uses, including Google Analytics and Google Adsense. Facebook is next with three.
Google Analytics was found on almost half of all loaded pages at 46.4 percent, while Facebook Connect was on more than a fifth, coming in at 21.9 percent.
Other companies that showed include comScore and Twitter.
And as will be seen in a future post, companies like Facebook enable advertisers to target age groups. Some of America’s best known employers, including tech companies, are targeting their employment ads – by age. Literally posting job ads only to those under age 38 or age 50, in what some law professors say is a egregious violation of Federal employment law. By preventing older workers from seeing job ads, these firms filter out older workers.