What are you talking about membership fees? That isn't the criteria for all Ponzi schemes you know? You don't sound like you know what a Ponzi scheme is.
It's you who doesn't know what a Ponzi scheme is. A Ponzi schemes requires new members to pay a fee to join. From Wikipedia:
>is a fraudulent investment operation where the operator generates returns for older investors through revenue paid by new investors, rather than from legitimate business activities.
The operator pays revenue to those who joined earlier with the fees received from those who joined later.