It's possible for a player to wager huge amounts and break even or even make a profit. In such cases I would expect the house to be unable to pay the referral fees. But in general the site expects payers to lose 0.5% of their wagered amount. They take 10% of that in commission (I guess - I don't know that I've seen that written anywhere), meaning they expect to get 0.05% of the wagered amount. And so they're giving 20% of their expected commission to the referring player.
That's my point. The system looks very risky and destructive (for the operator), unless he holds sufficient reserves. If the site is on loss (or breaks even, or makes a only a very small profit) for a longer period of time, the operator would have to cover ref payments from his own pocket (or his share of investment, which is even worse).
I notice that the 'Copy' button next to my referrer link doesn't light up when I hover over it like all the other active buttons do.
Works fine for me (firefox).