Been posting this around a bit. I feel that transaction authority is a MAJOR flaw in BTC for its stability in the long run. Basically, if heists keep happening and virii can rob you of all you possess, the currency lacks the level of faith that will attract a really schrewd following. So... I suggest two factor transaction authorization.
Basically as a part of wallet generation, a client side key is generated with a corresponding encrypted hash assigned to the address. So, wallet data wouldn't be enough to transact anything. I know wallet encryption provides a level of security as does truecrypt, but having a keychain would liken the transaction process to safety deposit box rather than a wall safe at home.
The level of sophistication would bring thefts to almost nil and make keeping a wallet file somewhere a way less risky operation.
It could lead to the development of more credit card like interfacing because your wallet data would be fine stored by an intermediary and one would need then only a keychain to validate a transaction. (hypothetically someone could make an RF keychain card with a fingerprint scanner so you could take your btc with you while you shop.
OR transactions could be partially transacted pending keychain verification allowing users to review their transactions and authorize only valid ones.
I believe this would go a long way to improve confidence in the currency which is vital to it becoming widely used.