During the August 12th episode of NUX Office Hours, a question came up about back buttons. So I thought it might be good to lay things out here. When using Newsfeed UX, you have two back buttons available: the back button for your browser and the back button within the app. I've highlight both in the attached screen shot.
In the example from the screen shot, the back button within the app takes me back to the Personal Info landing page. The browser back button could take me back to the home page, to a 403 error page, or any one of a number of other places - it all depends on the state of my local browser cache.