Because many are not aware of what goes on "behind our browsers" this is a shock to many. Certainly I was not aware of the extent of so many "tracers" - and the WSJ had done an excellent job of illustrating them.
Below are some of the examples of what websites are tracking and how:
And taking a single example:
Dictionary.com places 234 "trackers" on your PC when you visit their site. These trackers consist of more and more sophisticated software codes - cookies were the basic trackers developed long ago, but with the ubiquitous use of Flash in ads and software usage, there are "Flash" trackers left behind as well. Finally, as newer browser technology like HTML5 gets established as the new standard, even more sophisticated trackers called "beacons" are left behind.
Then there are the users of these "trackers". In our Dicionary.com example, only 11 trackers are "First" party trackers - that is directly related to fulfilling the request to Dictionary.com and perhaps additional cookies that allow them to keep track of when you return etc. 159 are cookies from a vast array of users - they could be Microsoft (from the version of IE Explorer, or from the Search engine that got you there like Bing or Google. Finally, there are trackers from any one of Third Parties that have reached an agreement with Dictionary.com (which is actually owned by web marketer IAC/Interactive Corp. The purpose and relationships here are among the most murky and little known and basically depend highly upon the goodwill of the "First" party dilligence. WSJ wryly notes that "These privacy policies do not generally apply to the activities of the third-party trackers."