What do you think, will it not be more effective if you would implement a sort of tier bonuses rather than a single and direct bonus? For example, you can make the first level sign-up bonus as 15 Good Dollars, 10 on second level results and 3 on the third and 2 on the fourth levels, this would encourage exponential and explosive growth as shown by many other networking companies before.
The focus is more on the social aspect, so direct referrals is probably better. It's also easier to think about which of your network might be interested than which friends-of-friends might be interested.
I can't readily think of any such companies that experienced lots of growth, who also had their own internal economy. I can think of PayPal (who used to give people a $5 sign-up bonus) or some credit card companies that do direct referrals also, but not MLM. It probably doesn't work for such companies.
Thanks for the suggestion, though. But now that we are out of testing we will increase the referral bonus to $45.00 GOOD.