By personally generated addresses, I meant addresses that $username generated. The ones where he has the private key / public key pair. Sorry for not being very clear about that. I suppose it'd be a bit silly for him to include addresses that he already has the private key of.

Technically, I could generate a key pair and have a totally legit address and it not be part of the blockchain (offline wallet). Unless you're saying every address possible is already part of the blockchain.