Well in theory couldn't any obscure exploit in the underlying framework (Solidity or related) be used to exploit contracts based on it? I think a comment from yesterday nailed it - that a system like this may be perfect for processing a repetitive, high volume of relatively low value contracts, wheres high value contracts may be better served by traditional systems wherein the Courts provide dispute resolution as needed. Broadly it would seem like Ethereum needs to isolate the potential for loss due to zero day exploits such that it is less than the savings realized from operational efficiency.