I feel much more comfortable using a certificate from restaurant.com. They automatically add 18% gratuity to your bill, so that there are no issues with tipping. And they structure deals such that you have to spend a certain amount, e.g. your $25 certificate requires a $35 purchase, ensuring the business makes some money. It's perceived as a gift certificate more than a coupon. Even better, they frequently have sales where $25 certificates are only $2.