University of Washington graduate student Parmit Chilana worked as an intern at the social networking giant last year, and, during her time there, interviewed Facebook engineers and design specialists to learn about how they build and deploy new features for the service. Chilana discussed her report, which she co-authored with other researchers at the University of Washington and Facebook itself, at the Association for Computing Machinery's Conference on Human Factors in Computing Systems, being held this week in Austin, Texas.

Facebook has an audience that would make user bases of even the largest software products seem small in comparison, Chilana explained. As of latest count, the social networking service has over 845 million users. And it is an audience as diverse as it large: Facebook supports over 70 different languages. About 80 percent of its users live outside of the U.S. and Canada.

"Even if only 1 percent of the users were dissatisfied, that would still represent close to 10 million users," Chilana said. "Most software companies don't even have a user base of 10 million users. So you can imagine the impact of [Facebook's] design choices can be enormous."

While its users may grumble about periodic privacy infractions or buggy new features, Facebook has largely been able to continue to increase its user base and keep them involved. About 50 percent of its users log on every day, and interact with more than 900 million objects that Facebook stores on their behalf.

Chilana sought to identify what perceptions those in charge of Facebook's user interface held about what makes for a successful user interface. She interviewed 17 Facebook employees -- software engineers, product designers and product managers. She queried them about the decisions they had to make when launching a new product or feature and asked how decision choices fit in with the company's business priorities.