This was not a "hack" per say where they get inside FB or inside Google and take their user lists. This was a keylogger installed as a virus. Passwords were taken off each machine as they were typed in.
As such there will be no notification because nobody knows exactly what accounts were taken except those that have them.The massive data breach was a result of keylogging software maliciously installed on an untold number of computers around the world, researchers at cybersecurity firm Trustwave said. The virus was capturing log-in credentials for key websites over the past month and sending those usernames and passwords to a server controlled by the hackers.
Generally in the event of a major breach everyone is forced to create a new password.