Part of the fun of Google+ is learning a new system and its new metaphors and mechanisms. The hard concept to wrap your brain around in G+ are "circles", which combine a filter for viewing incoming messages (like Twitter's lists) and access control for outgoing messages (like Facebook's private groups). It's sufficiently confusing that I never really know with any degree of certainty who will read anything I post without thinking about it pretty hard.
If Google knew who I went to high school with, it would be inviting me to make a "high school friends" circle, and it would be planning a reunion. But it's Facebook where that activity is going on, and Facebook where that particular circle of friends and former friends lives. It lives there not because I carefully and laboriously put it there but because Facebook has a group structure (however imperfect) that allows for shared group building, shared tagging of photos, shared lots of things.
On Google+ I have no visibility into what other people's groupings for me are. If you think about just that, it's remarkable – no one would add me to a mailing list and start sending me things without me knowing it, and no one adds me to a named Facebook community or even a Twitter list without that being at least nominally visible. Yet only Google knows what other people categorize me as, and as more random names show up in my "you were just added to a circle by…" list, the more that particular information asymmetry seems to be visible.
It has been wearying to try to make sense of circles. If you engage in the system, you are expected to classify and categorize all of your correspondents into some kind of bucket that describes them. Alas, real people are many faceted, and don't fit into any single oversimplified category or stay narrowly focused on one topic. More to the point, I can't stay on topic myself unless I have a separate place narrowly defined where I'm exploring a topic rather than just vacuuming up something interesting.
Google+ circles have cut into my sleep, and that's why you see circles under my eyes. I'm better off resting up and spending the time creating things rather than figuring out which tiny bucket to sort them into.