I like the idea. How do you distinguish between a real referral and someone creating multiple accounts?
IP? MAC address? Email or SMS verification? Check how Protonmail is doing it. It would add also additional value to have the email address of each user registered to the account.
It is not the geeknet that matters to the people it is the trashnet like Facebook and co... Geeks are still living in their own world, the new geek hype is augmented reality.