If you e-mail a document then you make a copy of it at that instant, but if you send a link then it is updated as the original is updated and the copy is made not when it's sent but when it's received, which I'd consider to be two very different things.

"Sharing" with a group of people like in Facebook (where each one can essentially change the nature of the thing in real time by commenting on it or liking it) is also somewhat distinct from the other two because it makes a send-time copy that can be changed (in limited ways) by people other than you in possibly unpredictable ways.

The problem is that share as a verb is a bad metaphor for resources that can be replicated without limit; publish (or send, broadcast) is the right metaphor for that process when seen as an instant, one-off action.

Now shareD as a state is how the metaphor makes sense, for content stored at a common resource where one can take it back later, like your profile on a social network. So a better use that would hold the right nuances would be:

- Publish for making copies of the content and sending them to channels where one doesn't have control.

- Shared / Private for the status of content on channels on which you keep control to change that status.

Unfortunately, the needs of social sites (that try to make as much shared information as possible, and avoid people to withdraw it) have promoted the current confusing usage and spoiled it for all.