You may have noticed that you cannot share some posts by your friends on Facebook; you can like them, you can comment on them, but the share button does not exist.
Julia Homewood explains the rationale behind it: “The idea of the “Custom” setting is so you can hide what you’re posting from certain people, which is what you want and are doing. Because of that, facebook won’t allow your friends on that custom list to share it with others because you have asked it not to by setting that post so that only certain people can see it. Therefore if facebook allowed your friends to share it, they would be violating their privacy settings and not doing as you’e asked. Basically, if you set a post to custom because you don’t want a certain person to see it, and then facebook allows that post to be shared, it could then be shared by one of your friends with the very person you didn’t want to see the post in the first place. do you follow me? It’s a bit confusing, I know.”
At first glance, this may make sense; especially for personal stuff, your photos and videos, places you have been, or your favourite books and movies. However, it does not reflect the reality for the other not-so-personal stuff, news articles, political pieces, and anything available to the public. Besides, the visibility of personal stuff, is already governed by privacy settings; hiding the share button should not have any real effect.
Imagine a person who shares an article by Amnesty International about human rights violations of his native country. He wants his trusted circle of friends to read the article, and probably share it; he may fear getting persecuted for criticizing his government. He cannot and does not want to hide the article itself; he just does not want everyone to know that “he” posted the article on Facebook.
I hope Facebook realizes that the ability to Share and the Visibility of a post are very different concepts and should be treated differently to ensure privacy without compromising usability.