[dpapathanasiou]

"Although I am skeptical the Groupon user base is a highly desirable group of customers, few people have actually made a convincing argument that shows they don’t return in significant numbers."

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.).

[elic]

In most markets, the waitlist to run a Groupon promotion is so long that it's tough for a business to dictate terms.

That is a good reason to run a promotion with a groupon-clone.