My initial thought was rather (for example) when a referral has earned you 1,000 gold you can send him 50 gold (5%) this will need to be done manually by the referrer
And this in levels, next would be if he reaches 10,000 gold and he gets 600 gold (6%) and so on

But working with daily bonuses as to say, I'm completely against this, this alone to discourage multi-accounting
And yes I could sum up more reasons
All the ideas I give or will ever give will be only benefit the honest members and will make the life of people trying to exploit the system very hard