While Americans celebrated a long Labor Day weekend, millions of people in China enrolled in a giant experiment in the future of fake video. An app called Zao that can swap a person's face into movie and TV clips, including from Game of Thrones, went viral on Apple's Chinese app store. The app is popular because making and sharing such clips is fun, but some Western observers' thoughts turned to something more sinister. Zao's viral moment was quickly connected with the idea that US politicians are vulnerable to deepfakes, video or audio fabricated using artificial intelligence to show a person doing or saying something they did not do or say. That threat has been promoted by US lawmakers themselves, including at a recent House Intelligence Committee hearing on deepfakes.