I would love this. Though Referral candy is a viable addon. I've found their attribution to be somewhat sketchy.

Hey fellow entrepreneurs!

Thanks for voting on this feature. I'm stoked to let you know that it is now live.

See details here: http://changelog.subbly.co/refer-a-friend-campaign-tool-33522.

You're hearing it first! Please take it for a spin and provide any feedback.

Thanks again for voting and contributing to what Subbly is today. Wouldn't be the same without you.