so authenticated relays with access determined by membership in the circle? 

 I'm still thinking about this. I guess relay-based  communities are the new circles.

Do I even need a list event, for this? I can just use the whitelist on the relay, but then the list isn't publicized and I wouldn't be able to auto-update the relay list, just by adding someone to the client list. I'm using the client list as a controller, basically, but it's a redundant list.

Can the relay publish the whitelist, upon request? Could there be direct manipulation of the relay list from a client?

nostr:nevent1qvzqqqqqqypzplfq3m5v3u5r0q9f255fdeyz8nyac6lagssx8zy4wugxjs8ajf7pqyw8wumn8ghj7cmgwf5hxarsd9kxctnwdaehgu339e3k7mf0qyfhwumn8ghj7mn0wd68yt3jxyhxxmmd9uqzpwn04mj0j9kpja6z747gjwyw287reffghetm7xtjq5fkgcfax55lk4cg8y 

 So one relay per circle?
Is this similar to communities in ditto? 

 Ditto communities aren't 1:1 with a relay. 

 I see. Thanks.