alt Hacker Newsreal world social networks have agency if you define ephemerality as agency. It's an accident of digital platforms that nothing is ever forgotten, not a feature inherent to normal human relations. In the real world you drop phone numbers, you forget events, unused relationships atrophy. And that's not a bug, forgetting is a feature. For anyone who isn't convinced of this, Black Mirror did an admirable job in its first season putting the pathologies of social technologies on display that record everything.
It can be argued that humans actually hate forgetting things. That's why we invented writing. Spoken language lets us share arbitrarily abstract thoughts with others. But human memory is imperfect, so spreading knowledge or memories through word-of-mouth is unreliable. Writing lets us preserve that information as intended by the original author, potentially indefinitely. That's also why we always wanted to be able to record and play back what we hear and see, and our civilization only fairly recently, in terms of history, got advanced enough to have technologies to do that.