Re: [ANNOUNCE] Bitmessage - P2P Messaging system based partially on Bitcoin
Oh, that's a GREAT place to put the address book. 
It also holds other people's public keys, the network object inventory, your subscriptions, and your whitelist and blacklist. So it is reasonably logical that it would also hold your address book.
Can you, maybe, put some of those things into user.dat? It kinda sucks losing that file when you receive a corrupt message, and would make backing up much simpler. Plus you maybe would be able to encrypt and password protect that file to keep it from being stolen and someone else using your identity or listening in, which I guess would be simpler than encrypting the entire message db.