That was the feature I loved about Google Plus, I used it extensively when the service was growing. But no one else went to it regularly enough. CS Friends, Video Game Friends, RPG Friends, Soccer Buddies, Family, Immediate Family, Colleagues (several for several different jobs). I could easily post things across circles that would appeal to that circle. Vacation photos go to family and some friends, most don't care (or need to see it). My nerdy tabletop RPG posts went to those friends who cared about it. CS/programming topics went to those friends who cared about it.

You just made me realize that this is implemented in Discord but very poorly. I have difficulty deciding where I should post a meme to get it to the people that will like it. Maybe I'm just on too many Discord servers...

Well, the other problem with Discord is that people have to opt-in to the groupings. Circles were publisher driven. If you were in my CS Friends circle, that was just where I categorized you. It was not akin to a FB group or a Discord server. In those, you have to accept some kind of invitation into the grouping, and you're made to communicate with everyone in the group/server. Circles were one way, from me to the circle. For a circle member to publish to all the same people they'd need to be connected to all of them directly in G+ and create an identical circle.

This is the same issue as group messaging in most instant message type systems (including SMS/MMS). It's forcing a full connection between all participants, when really we may only want a fan-out structure.

I haven't used it much (not as many people on it in my social circles) but WhatsApp's broadcast lists are like G+ circles in this regard.

Well, the circles feature as implemented and documented by Google managed to confuse even me and I thought I understood it early on.

XMPP roster groups

xmpp lol. Great protocol, terrible clients.