@laemeur I guess Katy Perry, just like her website, would likely have a mostly single-direction feed. Probably her feed would _be_ that from her website, maybe categorized with hashtags or grouptags. Or object_type={note,photo,video,blog}. Incoming notices would be ignored unless she subscribes to the user.

Users don't register to her node of course, so her 85M users are split into ~850K nodes with ~100 fans per place (since people use their accounts with the instance of their local football club's or hackerspace's or youth centre's or neighborhood to follow Katy Perry). Fans interact with each other through the localized !katyfansuk !KatyGoesSuburbanNY etc. groups that form through local group communities.

When Katy Perry writes something, the message is distributed once per hub of users.

I don't see any forthcoming issues if we naturally form Dunbar Groups (a term I just made up for groups primarily sized by Dunbar's Number: https://en.wikipedia.org/wiki/Dunbar's_number)