Ring signatureOne of the security properties of a ring signature is that it should be difficult to determine which of the group members' keys was used to produce the signature.
1. Good thing for hacker(one member of group) to wipe out your wallet by modifying orginal transaction and send all your XMR to his address.
2. How can you guarantee, there is no miner or passive listener who is building unobscured private blockchain and sell this data ? (why not to store internal data unobscured when it takes 6 times less space than monero blockchain)
3. How you can prove that you really paid or even did not want to pay.to hacker :-)
Risto, it looks to me that you bet on bad horse.
Edit:
Ring signatures are similar to group signatures but differ in two key ways: first, there is no way to revoke the anonymity of an individual signature, and second, any group of users can be used as a group without additional setup.
Once I know your PUBLIC key I can add you to my GROUP (adding my and your public key together). Then create ring signature and no one knows who signed message you or me. Then I can fork blockchain !!! (maybe even from genesis block)