The 16-year-old child of Slack and Flickr co-founders has vanished - with fears the teen has disappeared in a crime-riddled neighborhood. Mint Butterfield, whose father is billionaire Stewart Butterfield and mother is Caterina Fake, who both founded photo-sharing website Flickr together, is thought to have vanished while in the San Francisco Tenderloin area. The teens dad is also a co-founder of team-messaging app Slack while her mum is a successful entrepreneur who was the chairwoman of Etsy.