Self-sovereign identity is probably the most viable use case at the moment. No third party needed to manage your identity, replace keys, and broadcast updates to the world. Additionally adding the dimension of time, where you can differentiate between something signed while a key was active vs something signed after the key was retired.

Some argue this is the only data necessary on-chain — all other application data can remain in normal data stores while the identities interacting with that data are immutable and auditable.

Laying the groundwork for a lot of neat stuff https://identity.foundation/working-groups/identifiers-names...