I think the primary value from having a public hash chain in this case is that Facebook can't really do malicious things secretly. If they were to perform the procedure you describe, it would require very publicly listing all the accounts they are devaluing, and it isn't actually obvious that the impact on the value of the coins in those accounts would be significant. The value of the USD didn't instantly drop when it stopped being backed by the gold standard, and a coin that Facebook refuse to trade for cash would just be a "fiat" version of the currency, which could definitely retain value.
Today, when PayPal or Patreon shuts down an account, we only find out if that person complains and anybody pays attention. I imagine creators might prefer a platform that doesn't have obvious ways to easily shut them down, and where Facebook can claim to a court that doing so requires fundamentally compromising the security of the system.
Today, when PayPal or Patreon shuts down an account, we only find out if that person complains and anybody pays attention. I imagine creators might prefer a platform that doesn't have obvious ways to easily shut them down, and where Facebook can claim to a court that doing so requires fundamentally compromising the security of the system.