I like that.  Then it is less visible to everyone joining.  Possibly take 3% out of the curation rewards pool and 7% out of the author rewards pool to fund the referral reward program.  I feel like the rewards would have to remain on a single level kind of like how DirectTV or a lot of companies do referral programs.  It if spans multiple levels then people will get an weary feeling when being pitched to join because they will think it is Multi-Level Marketing.  The psychology of the platform could certainly change from it but I think if it was primarily done with affiliate links it would be a little more in the background and not an in your face pitch.  I signed up more than 30 people for Coinbase through their referral program.  I pushed the traffic there with free Google Adsense credits!  Heheheheheh