Stack Overflow lets Facebook track users across their sites

Most end users are ignorant of what is being done with their data and the risk associated with what these sites view as non-PII (personal identifiable information) and how, in fact, the data can be matched (too long to get into) to reveal specific user details (including PII) without the user being aware. All these sites are data mined for non-PII and put together and this data is utilised and sold. Fun Fact Two: I live in Australia and not only is our internet appalling, but our government shows a flagrant disrespect for basic human rights, including the right to privacy.

Source: meta.stackoverflow.com