The Wall Street Journal starts a series on what companies are doing to track consumers to make money online. Some of the common tactics:

The study found that the nation’s 50 top websites on average installed 64 pieces of tracking technology onto the computers of visitors, usually with no warning. A dozen sites each installed more than a hundred. The nonprofit Wikipedia installed none.

Tracking technology is getting smarter and more intrusive. Monitoring used to be limited mainly to “cookie” files that record websites people visit. But the Journal found new tools that scan in real time what people are doing on a Web page, then instantly assess location, income, shopping interests and even medical conditions. Some tools surreptitiously re-spawn themselves even after users try to delete them.

These profiles of individuals, constantly refreshed, are bought and sold on stock-market-like exchanges that have sprung up in the past 18 months.

If you are using the Internet, expect that people are “watching” you and trying to figure out how to make money off of you.