woothemes/woocommerce — pull request #788 by GeertDD (2012-03-12 10:05:40+00:00)
Title: Added option to globally enable/disable the use of coupons

One checkbox added in the admin. By disabling coupons globally, the coupon form(s) get hidden and no coupon discounts will be calculated in the cart.

Needed to implement this for a client. I think this is a useful feature.