The user experience of screen sharing could be improved, such improvements would be greatly appreciated:
Add a colored prominent frame around shared area (desktop, window, or application) or some other indication so that the one who shares can see that their screen (or other selected area) is being shown to the other party.
Add a button (that is always visible to the one who shares) so that he or she can stop sharing at any given moment, including an event that is generated when this takes place.
Provide a parameter that will allow running screen sharing in desktop mode so entire area is shared without prompting the user to select the shared area. This can contribue to clearer and quicker user experience.
When closing the sharing application the focus should not be returned to the shared area as this is confusing.