How to make an unprofitable Groupon campaign successful
blog.eatmetrics.com
blog.eatmetrics.com
It's probably better to use that as a starting point: i.e., assume Groupon customers are not the best demographic, and design the Groupon discount accordingly (only a modest discount on a higher-priced good or service, e.g.).
That is a good reason to run a promotion with a groupon-clone.
I think an important factor to note is Deal Expiration date. Many businesses only give customers 1-2 months to redeem a certificate, if you span this out across a year you will save yourselves a lot of energy when the Groupon is about to expire.