During his company's quarterly earnings call on Wednesday, Facebook CEO Mark Zuckerberg admitted the company hasn't do enough to prevent its tools from "being used for harm." In the West, conversations about that harm have mostly taken shape around privacy concerns in the wake of the Cambridge Analytica revelations. But in Facebook's developing markets, that harm has come in form of violence that's even turned deadly. The World's Carol Hills interviews New York Times reporter Amanda Taub, who co-wrote an investigative piece about how content that went viral on Facebook led to real-world deadly violence in Sri Lanka.