Some type of embedded auditing or some type of way to ensure that balances held across exchanges is frequently confirmed against the blockchain...is that even possible?
I do think it is desirable, since, out of control, fractional reserve banking is a bad deal for the masses, and always the biggest benefit to the 'already-rich.'
The answer is systems where the depositor continues to control the private key or part of a multi sig.
That would be good. I am wondering what the lowest level in the protocol / implementation would be that something like this could be achieved. The lower the level, the less trust required=better IMO.
Pretty sure multi sig is in the core protocol just not implemented yet. But develpers will be extremely cautious so don't expect it anytime soon.