The complaint has been investigated and
resolved to the customer's satisfactionResolved GreenBackStreet.com — Rebate scam
resolved to the customer's satisfaction
The idea that it is a unsustainable pyramid scheme is interesting, since people sign up as free members. What can they be scamming you out of?
In the classic pyramid scheme, the people at the bottom of the pyramid are paying the people above them (and no one is left to pay them). The last person referred still gets cash back on their shopping. They are out nothing. They are shopping at reputable retailers, paying the same price everyone else does, and getting rebates.
I have compared the stores on their site with the same stores found through Google or Yahoo. They are the same sites with the same prices.
If they have sites you shop at (among over 1000 stores), you can save money by getting the rebates.