Throughout 2014, students at Colgate University in central New York were outraged by a slew of racist comments. They didn't know who said them, just that they came from people on or close to campus. That's because the offensive remarks appeared on Yik Yak, an app that shares anonymous posts with those nearby.

Yik Yak, which allows users to reach other users within 1.5 miles, is the latest social media craze on college campuses, and one that can send a school into an uproar with just a few vicious posts. Students protested at Colgate in September , arguing that the racist messages circulating on Yik Yak were symptomatic of larger diversity issues at the school.

Those posts became even more hateful after students demonstrated in December in response to the deaths of unarmed black men Michael Brown and Eric Garner. Some students were singled out in the "yaks" for physical threats.

In response, some Colgate faculty members had an idea: to bombard Yik Yak with positive comments attached to their real names and clean up the local forum by example. More than 50 faculty participated during the Dec. 12 experiment. But by the next week, biology professor Geoff Holm said, the posts had returned to their usual tone.