Yes, I have to admit that during testing, I have spotted several errors and these may cause financial losses. Because of this, I have even deleted some features which many people consider useful (such as BTC deposit/withdrawal).
Security is a key concern for a financial system. I totally agree with your point.
The Bitcoin market is filled with exactly highly intelligent people. I will definitely pay attention to every single detail.
(If you see any bugs please email me. I will definitely appreciate that!)
Doing your best probably isn't enough. To have any hope you'll have to hire expensive security people and buy lots of insurance.
All you need in order to be exploited is to be using software with 0day exploits. Many known exploits are not public. In a very real sense, you are only protected to the extent that you are a small target.
As the potential payoff of a hacker approaches $1 million, the likelihood of being hacked approaches 90%. Software really is THAT insecure and bitcoin thefts are not prosecuted making it basically risk-free to steal bitcoins.