A couple coworkers and I did some edge case testing of the circles/sharing features this morning. In most scenraios, it worked in ways we expected it to work, but there seem to be some idiosyncrasies in how G+ handles posts that weren't immediately obvious.

One of the more surprising things we learned is that visibility settings in individuals' profiles seem to control how messages propagate through those individuals. We set our test up so that I was in a circle with coworker A, who was then in a circle with coworker B (but I was not in a circle with coworker B.) My expectation was that, if B then posted a message to his "extended network", I would see it in the "incoming" bucket in my activity stream, but that didn't happen. It turns out that in order for that propagation to happen, A had to change his profile so that B's existence in his circles was visible. This behavior kind of makes sense (especially if A doesn't want his association with B to be known) but it certainly does limit the extendedness of the "extended network."

Another thing we noted was that if you post something to someone in a circle and then remove them from the circle, they can still see it -- it doesn't go back and erase history, unless you delete the actual post. That's probably the way most people would expect it to work, but it could have gone the other way I guess.

We also stumbled across the "disable reshare" option in the sharing UI, and I kind of like that. Doesn't prevent someone from cut/pasting, but in a circle of people you trust, it could be useful.

Anyway, there are a lot of moving parts -- hopefully someone will (or has) put together an easy-to-understand cheat sheet so people know who sees what in all of the various combinations of post types, profile visibility settings, and circle memberships.