Data mining is a subfield of computer science that uses a computational process of discovering patterns in large data sets, involving methods at the intersection of artificial intelligence, machine learning, statistics, and database systems. The overall goal of data mining is to extract information from a data set and transform it into an understandable structure for further use.
Facebook is computer scientists main source of data mining information on the Internet. Facebook “likes” can reveal personality, gender, and sexual orientation solely based on pages, 
organizations, or people someone might “like” on Facebook. In fact, in 2012, Facebook bought data from 70 million households. This information was used to track user’s behavior to better advertise to them.
*(If you’re curious, you can visit youarewhatyoulike.com and see exactly how much your Facebook “likes” can predict about you.)
In her TED Talk, “The Curly Fry Conundrum: why social media ‘likes’ says more than you might think”, Jennifer Golbeck informs Internet users that scientists can predict A LOT about a person through what they like and share on the Internet. Mechanisms have been developed to accurately predict a user’s political preference, personality score, gender, sexual orientation, religion, age, intelligence, and more! (This is a prime example of data mining.)
One example Jennifer Golbeck mentions in her TED Talk is a Forbes article, “How Target Figured Out a Teen Girl was Pregnant Before Her Father Did”. Essentially, what happened was, Target sent a flyer to a 15-year-old girl featuring coupons and advertisements for baby products. As it turns out, Target has the purchase history of hundreds of thousands of customers that is used to data mine. Target can then used this mined data and determine whether someone is pregnant or not (and even the due date). The important thing to note is that Target did not data mine obvious purchases, like cribs or baby clothes, but rather looked for when someone would buy extra vitamins or a handbag that could hold diapers. While these items do not seem too important by themselves, when they are bought together in the context of thousands of other people, it starts to reveal a pattern: pregnancy.
Some creepier ways companies can data mine information from you can include:
- Companies using retina trackers to see how your eyes move in the store
- Advertisers watching your tweets to better market to you.
- Department stores tracking your smartphone to determine how long someone stayed in each section of the store.
- Amazon using cookie tracking to analyze where you’re browsing and what you’re looking at.
Just to name a few.
Grace's Civic Media Blog 