I had some posts that were originally private that I wanted to make public. I was sad to discover this the hard way:

You can’t edit a post’s sharing settings after the post has been shared. However, you can delete the post and share again to different circles.

http://productforums.google.com/d/msg/google-plus-discuss/CuoDsOjUO64/qDQdXt-tIbcJ — You should be able to change the sharing options. Even Facebook can do that!

Manage your posts - Google+ Help

Eugene Crosser July 08, 2013 10:16

You can also reshare your own post to a different set of circles.

Changing the sharing is actually rather difficult, conceptually, at least it is difficult to narrow the set. What do you with those who’ve already seen the post, but are now excluded? What do you do with their reshares? Shoot all witnesses? ;)

That said, making an originally private post public should be possible.

Michael K Johnson July 08, 2013 10:27

In my case, I just wanted to make the posts public (expanding the sharing should be possible even if restricting it is not) and wanted them to be searchable, not show up as new posts in people’s streams. I really didn’t want to subject the initial recipients to a stream of reshares of the originally private posts. (There were quite a few…)

So an action “expand sharing” would make sense if they didn’t want to deal with the hard cases. It seems obvious to me that reducing sharing would “break the link” with reshares. It’s not like the problem of inconsistent view doesn’t already exist, as deleting posts gives the same problems but they allow deleting posts.

Eugene Crosser July 08, 2013 10:36

I agree that expanding is possible and useful.

There still may be difficulties, like you’ll probably want to bump the post to the top of the stream for the new recipients, but not for those who’ve seen it, and it may be a non-trivial technical task (depending of the existing implementation). But they are technical difficulties and can be solved.

Eugene Crosser July 08, 2013 10:50

There may be a better solution: make reshares not visible to those who’ve seen the original post or an earlier reshare of it. That would suit your need, plus save the readers from seeing the same post reshared by different people in their circles.

And by the way I have a feeling that G+ is already doing it in some form.

Michael K Johnson July 08, 2013 11:04

I don’t want to bump the post to the top of the stream for new recipients. They are older. They should show up where they would have been, and only if people scroll that far back, or if they search for relevant content.

Also, I just saw today someone else’s inadvertently private post, and then saw the public reshare. Since they will accrete different comments, you suggestion to make reshares invisible would have potentially unfortunate side effects.

Imported from Google+ — content and formatting may not be reliable