Referrals, Groupon practices

Hi all, my company is hoping to implement a referral program similar to Groupon's.  Specifically, we want customers to receive company credit when they refer new business to us, triggered by a first time order for a new customer.  We want this program to work whether order is entered in the UI by a sales rep or placed through our site via a customer's unique "referral link."

We do not want to use the Sub-customer functionality because of the accounting nightmare it creates. Further, we want this program to be as flexible as possible (dollar amount not set in stone) and we'd like to notify the referring customer automatically on credit creation.