When adding a coupon its far to easy for an admin to add a coupon and have it selected as "No Coupon" instead of "Specific Coupon". This means that if the admin accidentally sets it to be "No Coupon" everyone eligible would get the discount without entering a code.
What is the best way to protect against this? Is there an extension that will state how many customers the promotion might apply to? Is there an extension to add a JS warning before the admin hits save?
There are a lot of things that you can mess up with your admin user account, not just setting a wrong price rule. Owning a Magento admin account is a big responsibilty.
I think this is just as risky as accidentally adding a wrong product price (for example setting a price to 3.00 (3) instead of 3000 etc). This can have some bad impact on your business as well.
IMHO the best way is to restrict your admin users only to those areas/pages which they really need to see/work on to limit the "attack" (in this case: "mistake") area.
