Here are some more thoughts. I'm thinking about private marketplaces on top of the Nxt blockchain. Products are visible only to the users of the marketplace, not to everyone viewing the blockchain.

EDIT: I deleted the previous idea. This is a simplified version. Marketplace name = password.

On the startup screen of the NxtPrivateMarketplace software the user enters the marketplace name, which also acts as a password.

This is less secure than having the program generate the password, but the result of the marketplace name getting found out by outsiders is not as catastrophic as somebody hacking your brainwallet.