These days, almost all the services on the web are tied together with a complex series of partnerships and multi site logins. With so many sites all sharing and swapping your information, they would be crazy not to utilize this to their advantage. The way that many sites do this, is through a method called "targeted advertising." It's just as simple as it sounds. Targeted advertising uses information and statistics that various sites have gathered to let web advertising companies know just who YOU are. This allows websites to show ads that are far more relevant to you, and create a more personal experience. But is this really such a good thing? The information sharing can go pretty deep, with some pretty personal information being given to factor into a potential score that ad companies use. Anything that could even potentially be analyzed is ran over with a fine toothed comb. Users cease to be users, and instead become scores, matched to various thresholds that companies use to determine whether you re worthy of their time and effort. But the ad companies are not the major focus here. What's more important to know are how sites portray you to these various companies.
Facebook is typically on the fore-front on social experiments and information mining of its users. Facebook tracks both your likes and comments on posts, and targets posts of a similar nature back to you. If you like a single post by a toy manufacturer at one point, then there is a high likelihood that you will get an increased amount of toy related ads and posts showing in your Facebook feed. Friends will also receive more, as Facebook assumes that circles of friends share similar interests and are therefore more likely to be swayed by the same advertising. What you like, comment, or even VIEW, adds in to an invisible score threshold that Facebook sells to ad companies to determine where you fall on their scale. They also distribute personal information such as your age, location, and profile notes like hobbies or relationship status. It even gives out your pictures, as your race, body type, clothing style, facial hair, etc. are all points that the company uses to calculate your worth.
Twitter is no stranger to your personal information either. Your public tweets are sold to companies for analytics in a whole range of subjects. How many users tweeted about a particular athlete is used to determine a range of how many paraphernalia regarding that athlete are produced. Record companies determine where the most people are tweeting about a particular musician to plan their tour locations. Twitter also looks at your phone apps to figure out your interests. Play a lot of Candy Crush? You may see an increase in similar game ads or related tweets. All thrown into a constant torrent of information that is sold to companies that has been aptly dubbed "The Firehose."
But Google is by far the worst offender. Google tracks all your search information, login times, passwords, user names, Google map locations, privacy settings, images, page clicks, page time, the list goes on and on. Google has consistently come under fire for these practices, as many claim it to be a gross violation of personal privacy. Google was under investigation for willingly compromising Gmail accounts to allow companies a peek at your private mail. Streetview cars were not just taking photos of your house, they were scanning for any information passing through public wifi signals that they could potentially tie back to you to in turn sell. Google has revealed that the privacy settings many sites or browsers uses have been bypassed by Google to gain more information. Setting your browser to incognito does nothing to stop Google's mining. Google also uses your comments or praise on any sites it can find to promote other ads. That means a comment you made two years ago praising a particular food brand may find its way into another users monitor through an ad. All the information you can possibly provide is stored by Google. While not all of it is used, it still exists in a server somewhere should Google decide to push the boundary even further.
So the question becomes "is it worth the ease of access and usability to allow these companies such unhindered access to our information?" Many people would say no. A large portion of these practices are not only intrusive, but are blatantly illegal, which is why they have put the companies under the eye of various court systems. And yet many people continue their lives with these companies gleaning their every action for marketing data, completely unaware that they are a walking statistic. Some are aware of these practices but are apathetic, seeing no reason why they should care about their information being gathered in this manner. And if that outlook proliferates, there may come a time when we are past the point of action against these practices.
Sources
http://research.microsoft.com/en-us/um/beijing/events/ia2011/ayman%20sigir%20_mike_v2.pdf
https://www.facebook.com/notes/facebook-and-privacy/ad-targeting-and-your-privacy-keeping-you-informed-on-ad-targeting-updates/517330291650191
https://support.google.com/adsense/answer/9713?hl=en
http://business.time.com/2013/10/08/twitter-is-selling-access-to-your-tweets-for-millions/
http://www.howtogeek.com/howto/25008/access-all-your-google-accounts-at-the-same-time-with-multiple-sign-in/
http://www.wired.com/2014/11/twitter-targeted-ads/
http://www.nytimes.com/2013/10/12/technology/google-sets-plan-to-sell-users-endorsements.html?pagewanted=all&_r=1&