I like how in Google+, when someone hits the reshare button to reshare your post, if you have limited the visibility of the post, the resharer may see a reminder to "remember to be thoughtful" about who they share your post with. I don't know what dictates, exactly, when that reminder comes up, but it appears even when resharing a post that has a visibility of "Extended Circles" (friends of friends). If the resharer does proceed to share the post, he can share it with any of the sharing options (including Google+ Communities) except for "Public." But what if the resharer is resharing a reshare? (And what if Sally were to sell seashells by the seashore?) The first screenshot below is of a reshare of a post. The warning comes up when trying to reshare it. The original post was shared to the public. When resharing posts on Google+, only the original post is shared, even if comments have been made by the resharer. So it is strange that when one reshares a reshare that was limited of a post that was public, he is presented with a warning and limited in how he can share it. The second screenshot below shows when a user proceeds to share a reshare.
Perhaps resharing a reshare causes the reshare that you are resharing from to be explicit in some way: in other words, the fact that that person has reshared that post is included within the reshare (of the reshare). As it turns out, who reshared a particular post is already public, regardless of the visibility they set to their reshares. A list of all resharers can be found in the post's activity drawer, accessed via the button to the right of the +1 and reshare buttons (which is present on original posts, not reshares). The only purpose the warning and the limiting of sharing options serves in this case is to slow resharing of the original post, which mitigates the ever present potential for someone to click through to the original post, open the activity drawer, and view the resharers, some of whom might, in some cases, not want the fact that they reshared the post to be more public than the setting they set for their reshare. But no guarantees!
Reshares and Mentions
It was probably just an oversight of Google's that the warning is applied universally, with no exception for reshares. But it was not an oversight to have the warning in the first place. Google wants you to be mindful of others' preferences when sharing limited posts, so the site presents you with a friendly reminder. Yet I have never been advised by Google+ that the act of my resharing something is public, despite only scant indication that this is the case. In fact, today, when I reshared a post to one of my circles, I think it was the first time I had reshared a post to a limited group (I usually share publicly), but even then, no warning presented itself.
Similarly, if you mention someone in a comment on a post, that person gets to see the whole post and comments thread, even if the post was not shared with him. Nothing presents itself to tell you to be thoughtful about sharing with someone to whom the post was not originally shared, in this case. However, posters can lock posts, which blocks resharing, photo tagging, and certain mentioning.* It appears, though, that the options to lock posts and to disable commenting on posts are only available on the desktop version of Google+. The second and third screenshots below were taken on an iPad (app and browser, respectively).
*When commenting on a locked post, one can still mention people to whom the post was originally shared.
Seems like there's no reason that those options should be missing. There's plenty of room. Even on the website, room could be made available if Google were to just choose whether it wants you to share a thought or add a comment. Make up your mind, already. Speaking of which, the iPad app has the slightly different wording of "Share Your Thoughts…" and the desktop version asks you to "Share what's new…"; did four Googlers get in a fight and this was the only way Larry Page could break them up? Or is this a secret data thing, and Google knows something about mobile website users that I don't?
+1ing on Google+ is as public as the post you're +1ing. I don't know whether Google explains this to first time +1ers. To Google's credit, mouseover text on the +1 button on websites reads "Publicly recommend this as [user's name]." On touch devices, when +1ing, a message pops up briefly indicating that the +1 was public, but this is far from adequate due in no small part to the fact that the message appears only after the action is taken, but also because of its subtle nature and duration. +1ing on Google+ itself (including the iPad app) affords the user no such mouseover text or message. If a user hides the +1s tab on his profile, all of his +1s follow the same rules except that the profile tab becomes hidden. Google might want to articulate that. Users who choose to hide the +1s tab on their profiles might think that doing so means: their +1s on external websites are private (because the +1s tab is just for those +1s), that all of their +1s are private and only the poster is notified of the +1, or that their +1s are anonymized (or that their +1s are anonymized except to the poster who gets a notification). Atop the +1s tab on a user's profile, there is an explanation of +1s, but it doesn't do anything to explain +1 publicness, and its "Learn More" link links to a page that also doesn't do much to explain +1 publicness (nor does that page link to this page on Google's support site which does a great deal to explain +1 publicness).
The +1 button on web pages does not automatically publish to the streams of those who have circled you. A publishing box is displayed when pressing the +1 button though, in case you want to share your +1. Facebook, on the other hand, publishes your Likes automatically, and if you disable that (if you ever find the setting), it only disables one type of Like (I think), as I complained about earlier. But Google isn't against annoying automatic actions as I explained in this post about a feature called Direct Connect which appears to be not working right now.
Seeing who a post was shared with
Those to whom a post is shared with on Google+ can see the other people to whom that post was shared, as far as I know, and in a sense (see screenshot above). For public posts and posts shared to extended circles, just that information is available to those who can see the post (the information that the post was shared to "Public" or "Extended Circles"). In the case of a limited post, people who can see the post can see linked profile pictures of up to 21 other people who can see that post. This is true even if a user hides who he has in his circles on his profile. It is also true if he has hidden on his profile who he has in particular circle(s). That means that even in that case, people who see his limited posts can see that he has a particular person in his circles (though no names of any circles are given), even if that person is in a circle that he has chosen to hide from his profile.
There's a reason users can see who a post was shared with. If you're commenting on a post, you might want to know who you're talking to. If a post is shared with over 21 people, though, viewers of the post will see "+ [number] more." In other words, in some situations, commenters get the benefit of knowing who they're talking to, and in other situations, they don't. I think that if I share a post with 30 people, but 17 of those people are in a circle I have marked on my profile to be hidden, then the shared with should see three linked profile pictures and "+ 17 more" (unless a person is one of the 17, in which case he'll see four pictures, one of himself). If a keen observer sees such a post, without two neat rows of profile pics, then he can tell that the poster has a hidden circle (or two), but he can't see who's in it, and I don't think this is significant, so I would propose this method as a solution. As for when a user sets his profile so that none of the people in his circles are shown, perhaps the thumbnail images should still be available to people who he shares posts with, for their benefit. However, Google should make this clear (with, again, allowing for hiding of individual circles that effect what thumbnail images are shown in posts; this combination will make Google+ flexible enough for my taste).
More Advice for Google
Make it known to new users the publicness of resharing and +1ing up front. My recommendation would be to do this right when a user gets an account. Remove the unnecessary warning and limitation for resharing of reshares, but implement it on mentions. Add the lock and disable comments features to the apps. I don't want to hear any excuses about how it would mess up the design or something. Implement my suggestion about profile pictures of people in hidden circles, and make the explanation of that appear when someone is changing the applicable settings on his or her profile.
I don't remember setting up my Google+ account all that well, and it was a long time ago, and the setup process could have changed since then. But I doubt there was enough explanation of any of this. Make it so. Don't be afraid that if you tell your users things, they won't use any of your features. Don't be worried that you'll inundate your users with too much information. This is a situation where you want to ask your wordsmiths in the company in how many words they can communicate X to users, instead of just assuming that it'll be too much information, and a bad user experience, and users can't handle it. If Google+ can be the network that's up front with its users and actually fixes some of these privacy "idiosyncrasies" (I'm sure I'm not using that word correctly), then they can start running commercials about it. If they start running commercials that are truthful, and really show how Google+ protects its users and makes them in control of their own privacy, that's a competitive advantage.
Here's another idea: if users really understand how your network works, they'll use it. People use the social network features of social networks, but not for everything. They're using things like Facebook chat too. They have a lot of choices. Here's a tip for Google and Facebook: if you want the world to be more open and connected, a sentiment I share, then put users in control of their privacy. If you want more openness, make the limited-view sharing really appealing to users (by letting them know what to expect). Strange, I know, but limited-view sharing is a different type of openness than public sharing. It's an openness among classmates and friends, and it goes beyond that too, because even though Google warns about resharing something that wasn't meant to be reshared, posts are only one side of the equation: there's no stopping the spread of ideas.