Google+ seems to pride itself on making it easy to decide what group of people you want to share things with. Circles are much easier to handle that Facebook lists, and they baked the choice of what Circles you want to share certain content with into every time you hit “share.”
In a Tumblr-esque move, they also have an option to re-share things that others have posted. Via someone else, I shared a message on my profile that said “Welcome to Google+, Mark Zuckerberg” (he, or an imposter, had quietly opened an account shortly before). I thought that was a little funny, and didn’t have much else to do, so I clicked “share” and it zapped over to be shared to my circles.
Now, I didn’t give this much thought until I checked out the original source of the post, where I could no longer see it! What happened is that he posted this thought with a small circle of people, one of whom “shared” it with her larger Circle which is where I saw it and shared it.
But after you are conditioned to think that your sharing is so under control (you have painstakingly sorted your “friends” into “besties,” “weirdos” and “potential employers”) that now you have completely forgotten or never even thought to consider that if you didn’t disable the re-share option, what you’ve spoken, perhaps in confidence, has the immediate potential to escape your carefully inscribed Circle and wander out onto the wider web.
Google’s help page actually acknowledges this oddity:
Unless you disable reshares, anything you share (either publicly or with your circles) can be reshared beyond the original people you shared the content with.
No real moral here, I guess. Just keep that in mind.