The events system is great an useful. However it would be very advantageous to have events, not just after something happens, but before so some custom action can be taken. In the case of an order, the context of the order could be inspected to ensure specific business/store rules are met. If not it could be rejected with a custom message to the customer etc.
In this scenario: https://www.nopcommerce.com/boards/t/47929/eu-vat-customer-with-invalid-vat-should-not-be-able-to-order.aspx
The vat number could be inspected and validated, and the order creation rejected with a custom message etc.
