SebaKL, I was trying to figure out what you meant, as I use it, but only just started getting an understanding of its usage. So I am digging deeper, but I am pretty sure what you said is the case. I started thinking about when I see it pop up and sometimes there are two sets of the icon. I noticed that two photos had been added by someone in my circles. Thanks a ton, I'm going to figure out how to have more control of it.
Sorry, I will rephrase that
When you register gmail account, by default you are automatically given number of other facilities / accounts. G Plus, Google Drive (cloud storage), Youtube etc... G+ has become the main profile for your Google everything, and soon, when you call people, they will see your G+ profile pic as your caller ID.
Even if you are not part of G+ community, other Android / Google users can see you there, as long as you guys crossed paths in a past, whether e-mail each other, have each other in phone book etc... Google finds that and recommend you to connect with people you are frequently (or at all) in communication with. I do recommend trying out G+, it's a kind of far more refined version of Facebook. Personally I follow bunch of photographers, automotive news, made few friends from like minded group of people. I find good stuff daily, and google is really clever in learning what I like, and serves me really all the news and posts up to my taste.
Anyway....With G+ becoming important google's platform, there are other features on the phone to make it all working seamless. AutoBackup uploads all your photos and videos to private gallery under your G+ account. And it does that as soon as you take a photo.
Auto Enhance look through your content, and make non permanent adjustments, without damaging the source files. If it's find number of photos of similar subject, it will try to animate it into images sequence, if it finds photos where colors, contrasts could be improved, it will do it for you. And that damn thing it's quite good at it
When all these happens, the phone then will inform you about these activities via notification, with the two small circles icon.
To turn OFF auto back up, go to Setting - Accounts - Google - touch the e-mail address, and un check Auto Back up. You may want to disable auto Sync features related to photos. This stuff can keep the phone busy, and munch on your data while the phone idles.
Then open G+ and view your Gallery, see if there are any photo albums created. You can delete them.
I guess that's it.
Let me know if you don't understanding something
cheers