More than 2,500 missing people have been found in Egypt because of work by the Facebook page Missing Children, which compiled a vast trove of photos and uses facial-recognition software to match faces to cases. The page collected the photo library with a campaign asking the public to photograph children begging on the streets. Using a Facebook grant, the page has expanded to a website with face-recognition tools and expanded to Romania, the first step of what it hopes is establishing a global reach.