As a recent case study on our sister site Subscription Site Insider revealed, marketing subscriptions via Groupon can be a fabulous way to raise sales. But never ever roll out nationally with your first shot, especially if you're a small operation. Pick a regional blast instead.Also, limit the number of deals so you don't end up like this poor baker, who had to make 102,000 cupcakes due to demand she neither anticipated nor was prepared to handle. Rachel Brown of Need a Cake bakery in the United...