Im not sure how the banks are handling it but i believe when a private persons bank account has unusal high transactions with many different actions they will be cautious. They will fear money laundering and will close the account because its easier to close the account than checking if its really money laundering. They have enough customers that wont make them such work left.

Then they check the other users that traded with that account and so on. If they make the work to ask back what it was about and they hear "Bitcoin" most banks will close the account. Bank Zachodni is a bank that wont close so fast. Thats why they is used for that.

I wouldnt advise using your normal bank account for transaction with private persons, only with exchanges. At least iam wouldnt want to risk losing the account i use for my daily live.