The spokesperson also said that the new rule applies to those "new to Messenger," and that those already using the app without an account don't need to do anything. However, some users have complained of encountering difficulties signing in after the transition -- the app apparently kept telling them that their account has been restricted. It's unclear if the change will have any effect on the tech giant's plan to make its messaging products interoperable, which will allow users to send messages across Messenger, Instagram and WhatsApp. A lot of people use WhatsApp, in particular, for the privacy and security it provides.