I tried to switch what server my account was on halfway through my GNU Social life, and you just can't; all your followers are on the old server, all your tweets, and there is no way to say "I'm still the same person". I didnt realise I wanted cryptographic identity and accounts until I tried to actually use the alternative.
That's also part of the interest I have in something like Urbit, which has an identity system centered on public keys forming a web of trust, which also lets you have a reputation system and ban spammers which you can't do easily with a pure DHT.