You surf the net under the watchful gaze of Web tracking networks. They record the Web sites you visit and your clickstream. They compile that into an anonymous profile,which they then market to various interested parties. Some are advertisers who want to deliver targeted ads to you. Others are insurance companies, credit card processors,or background investigators who want to run business intelligence software on this data and score it.
They discover that people who visit the same kinds of sites you like to visit tend to be bad credit risks, file more health insurance claims, or are involved in more employee lawsuits than the average bear. So you are denied that new credit card, your health insurance premiums shoot through the roof, or that job you coveted goes to the second most qualified person who applied. You of course, will be aware of none of this.