A referrel system
There should be a referrel system, where our customers can recommend our products to other people and either receive a coupon, or free product, etc. Maybe where they sign up and receive a unique code that is associated with their account, and then if anyone buys through their code, they receive some sort of compensation that the owner sets up.
On our Premium and Professional packages you can create and manage an affiliate program that allows you to track and pay commissions to customers and partners who refer customers to your store. Today you are limited to tracking and paying a dollar amount for commissions though, you cannot track and automatically credit coupons or free products even though you could still use the affiliate program to track this manually.