Actually I removed the EDIT part, because it is not logical to me. One public key must have one private key always. Bu one address can correspond to more keys because of hashing.

There are many people work on resolving and emptying the used wallets.

Especially they claim that addresses which start with "1" and addresses generated with secret words (thus brain wallet) are not secure at all. I'm not familiar with the details that much but this seems dangerous to me, because almost every system generates addresses using brain wallet method with 7-8 words. This makes the most addresses weak. There are really good DEFCON briefs in youtube about this subject if anyone is interested.