The same could be said for the sources. If you have the cable box on let's say HDMI 1, and you turn the tv off while viewing this source, the next time you start the unit it will still be on this source.
I'm not sure I understand your question all the way. Are you asking if someone can change your Source of the TV using the SmartHub? If so, the answer would be no. you can only manually change your source by using the remote or the buttons on the TV. May I ask what source do you currently turn on it? Also, what port do you have your cable box connected to?