Pokerstars was not operating like a fractional reserve bank, because it had segregated player funds to separate bank accounts. As in, it didn't have a "fraction" of reserves for the money players saw in their accounts, it had "full" reserves. It didn't have to go out and sell illiquid assets in order to pay players. It already had the money at hand.

If you want to characterize Full Tilt Poker's operation as a ponzi scheme, I have no problem with that. Full Tilt Poker was operating as a fractional reserve bank, and in addition to this it was siphoning assets of the bank to its owners.