It’s unlikely that Facebook or Google will give users the chance to encrypt chat that take place on their own servers to protect it from access by the company or by a court order, says cryptologist Bruce Schneier, a fellow at Harvard Univerity’s Berkman Center for Internet and Society.  “​​It’s a good thing, but it’s privacy around the edges,” Schneier says of Facebook’s encryption option. “Facebook doesn’t want you to do encrypted chat on its site that they can’t read.”

Source: Facebook Email Encryption Another Blow to Surveillance – US News