Mac OS X 10.7.5
ST2 build 2219 and ST3 build 3010
If you have Sublime Text set to remember files you have opened in between sessions with setting either "hot_exit" or "remember_open_files" to true and you have a file opened and then open it again in another view with `New View Into File` (from the `File` menu) you'll notice that the new clone view is in the same window as the original view. When you make edits to either the original view or the new view the other one reflects those edits as well. This synchronized editing makes sense because you're editing the same opened file within each view. Now, if you keep these views open and you then restart Sublime Text this synchronized editing still occurs as expected.
Now, let's say before restarting Sublime Text you placed these different views of the same file into different windows. The synchronized editing would still be fine but once you restarted Sublime Text the synchronized editing would no longer happen. The different views of the same file would forget about each other so that editing in one view would not be reflected in the other.
This also happens for new files you create but don't save to disk before closing and reopening Sublime Text.