Thanks for the genuine question. 

I suppose this depends largely on what implementation of a referral program the creator has made.

For programs which pay out directly on referral, the point of contract fulfilment is when referral happens and there is no need for contract to have a need for refunding advertisers. This is our goal implementation at the moment.

As for programs that may payout on sales, again we want this to be autonomous. This is a more complicated scenario. There are solutions that allow third party APIs (let's say paypal in this example) to integrate and fulfil contracts. One such example is Chainlink (https://smartcontract.com/) and we will surely be looking at integrating this in the near future.