Tracking Cookies
Tracking cookies are used to log long-term browsing records of individuals, creating privacy concerns for users. While there is no technical definition of a "tracking cookie," most tracking cookies share common characteristics. Tracking cookies, sometimes called "persistent cookies," have expiration dates that extend beyond the current session. Tracking cookies stay on the local computer for up to a year, logging the user's browsing history. Although tracking cookies can only record a user's browsing habits on the network that created it, some networks are amazingly expansive. For example, websites that post advertisements from Google Ads are part of Google's network. As a result, Google's network consists of literally millions of websites. To make matters worse, Google has the ability (and also the user's implicit consent) to bundle cookies into packages and sell them to marketing agencies. These agencies use this data about browsing behavior to send personalized spam. Users cannot protect their personal information from these advertising firms unless they disable cookies. Unfortunately, in this day and age, when tracking cookies are essential to the proper functioning of websites worldwide, it's extremely difficult for users to reject cookies and still reap the benefits of the World Wide Web.
References
Geary, Joanna. "DoubleClick (Google): What is it and what does it do?" The Guardian, April 23, 2012. http://www.theguardian.com/technology/2012/apr/23/doubleclick-tracking-trackers-cookies-web-monitoring (accessed March 15, 2014).
Microsoft Support Description of Persistent and Per-Session Cookies in Internet Explorer Article ID 223799, 2007
Microsoft Support Description of Persistent and Per-Session Cookies in Internet Explorer Article ID 223799, 2007