Agreed. Having a startup, YC or not, have full access to our bank accounts is not giving me warm fuzzies.
I've asked our bank to make all ACH transactions above a threshold require manual authorization to improve our risk exposure. While ACH transactions can be reversed, it wouldn't be pretty do be without funds during arbitration.
I understand why they want it, but I wish there were a better way than "here is write access to my bank".