Ability to block customers

We've had a few problematic customers in the past and told them to never buy from us again. We recently had a customer "threaten" us and we want to ensure he's never able to purchase from us ever again. Right now, I can lock him out of his account but he can always create a new one. There should be a way to block vile customers, permanently. In my mind, it should work on multiple levels; email address, name, contact info and shipping information. When a certain customer is blocked, the system records the information above and when someone tries to create a new account using any of the blocked information, it fails. The system won't let them complete the account/order. In business hub, when a customer is blocked, there should be something that flashes, pops up, or something, to let the operator know the customer is blocked. Maybe even a spot where you can write why the customer is blocked.