If you were on the internet in the late 1990s, you might remember companies like AllAdvantage that promised to pay you to surf the web. You could install a program that tracked your browsing and showed you targeted ads at the top of the screen; then AllAdvantage would give you a cut of the ad revenue you generated. These schemes largely disappeared after the dot-com crash.

Get in-depth coverage of current and future trends in technology, and how they are shaping business, entertainment, communications, science, politics, and society.