With PGP (for that matter, PKE generally), you always need the original recipient to stay alive and use her private key to decrypt.
With proxy re-encryption, you don't. So any use cases that involve Alice disappearing while others continue to be able to encrypt for Bob (even without knowing who Bob is or what his public key is) are good ones for NuCypher.
With proxy re-encryption, you don't. So any use cases that involve Alice disappearing while others continue to be able to encrypt for Bob (even without knowing who Bob is or what his public key is) are good ones for NuCypher.