One criticism I would make is that he's not clear about the end game. What happens when it comes to be payout time and he only has 75% of the amount he needs to make a payout?
Does he:
1) shut down, and keep the remaining funds for himself?
2) shut down, and make a final 75% payout?
3) skip this payout, wait for new deposits, then continue business as usual whenever there's enough to make a full hourly payout?
4) something else?
It would be good to have that clearly specified.
If my understanding of ponzis is correct, I would think that if new deposits slowed down, payouts would simply take longer and longer to fulfill.
It really depends on the operator.
"Bent" operators may decide to close the scheme as soon as the rate of new deposits slows to below the rate of outgoing payments. If their aim is to run off with the coins then it makes sense to stop when the available "haul" is as big as possible.
Even a legit operator may decide to close the scheme as soon as there are not enough coins available to make a regular payout. So long as that is announced up front I think that's OK. We just need to know what the rules are.
In this case I think he has said that he will run the scheme indefinitely, just skipping hourly payouts if he doesn't have enough to make a full payout.