We do have the same problem... Many users publish to everyone by mistake.
Or make it configurable, so it doesn't default to Everyone?
Just circling back around on this. There is no option to disable this currently. Even in the server has personal containers disabled the mobile application will present the option and only return an error when the user attempts to publish either to everyone or share with specific people.
Definitely an item that needs to be smarter and detect whether the personal containers are enabled for the various content types. Having the ability to turn it off completely in the mobile application would be a nice addition. The mobile application does a lot of checking for features like news so just some more feature checks with the settings coming from the server would be a good addition.