Has anybody integrated craft with a rewards system? Just wondered if anybody had done anything like this? Perhaps through zapier or a custom inetgration? Customers earning points or discounts through a Craft e-commerce site?
I don't think there's a plugin, but there's numerous jQuery or SaaS products that achieve this. 

For a Craft Plugin, you could hook onto the after purchase event and add a set amount of score to a user field.

e.g. if our field was score, after purchase we could add +30 to the score field. Then assign discounts based on the score field. e.g. if $score &gt; 30 assign 30% discount to products.

For integrations, you could easily just listen for the event and send some data via a PUT request to a third-party system.