Facebook Study Sparks Soul-Searching and Ethical Questions

Facebook’s study on users’ emotions shines a light on how companies and researchers tap the vast amount of data created online.

Internet companies including Facebook and Google routinely test adjustments to their sites for reasons including prompting users to click on more links, or more ads, which are the companies' main source of revenue. The companies show different versions of a page to groups of users, and monitor how users react. In the industry, this is known as "A/B" testing, for the two versions. Early A/B testing focused on issues like the colors of a website.

Now, the process is used "to get people to do exactly what a company wants them to do on websites, in apps and in life," Nancy Hua, chief executive of Apptimize, a startup that conducts such tests for other companies.