I often want to record calls among a small number of participants, for posterity. It's often related to open projects, so I don't mind the small chance that a random person from the internet might join the call.
I feel that Hangout On Air events would be great for this, but it's not totally clear how to host them in this way. (I tend to default to unrecorded Hangouts, because they're simpler, but then we have no records of the call to share with others.)