Obviously we would completely purge any public keys for accounts with zero balance and with no aliases.
Is there any way this could lead to a Sybil attack?
If it is possible to create a "new" account *with* a public key (as an atomic operation) then this shouldn't be a problem (isn't that coming?).
Would the account with a zero balance and a full public key survive the blockchain pruning event? Perhaps I'm not understanding fully, but it looks to me that it wouldn't.
That is, the public key would be discarded on an empty account. No?