Nice Idea, but not well executed. There are a few big issues:
1) An advocate can limit the FB share to just themselves (by selecting this option in a pull-down menu above the share button) and still collect the discount. If someone wants to game the system that way, it's very easy and obvious to do.
2) The FB share looks bare bone. There does not seem to be a way to influence the image FB pulls into the post, nor can the post be pre-populated with a message. What good does a bad looking post?
3) The Coopt reward for sharing uses a discount that you have to create manually in Shopify. That discount's validity is not tied to successful shares. Therefore, if the discount code becomes public knowlegde (e.g. by someone posting it somewhere), anyone can redeem it, sharer or not.
These are substantial short comings for a referral app, where the basic idea must be to reward for performance. So we deleted the app.