It's the weakest point of the system, you are absolutely right. Trust shall be accumulated due the time of stable work, but it will never be enough.
The main point: we are developing it and we have profits from BitMoney stable work and popularity. Absolutely no reasons for us to harm the project or our clients interests.
I hope that build-in exchange will not be the main BTM market, so users will not have to rely upon us in this point either.