It's great that you brought up the referral system idea!
I'll re-iterate what I proposed not so long ago. I think it would be useful to run an initiative with rewards given for onboarding someone who makes an introductory post with their picture on it holding a piece of paper with the date, account name and other information written on it and that person stating that they were onboarded by the person to be rewarded. Additional rewards for reports proving that those same people are still posting after X months and that they have powered up some moderate amount of HIVE.