According to a podcast I listened to once (can't remember the source but my best guess is Mixergy), the best way to utilize Groupon is to have a plan for customer retention and upselling. Not just attract a bunch of coupon-hunters who just want to get something for dimes on the dollar.

I believe the example they used in the podcast was sky diving. Lots of possibilities for retention ("get a rebate on your next jump if you sign up for membership") and up/cross-selling ("we have t-shirts").