Still unsure if its a scam or not.  ive had a pretty close look at this pyramid type reward structure and it seems to me that if your in it from the start of the block then theres every chance you'll more than get ya money back, if , on the other hand, you join mid way or even a bit earlier then you cant recieve the rewards you need to be able to double up at the end of each block! You will have to fork out of your own pocket to make the short fall , If you look towards the end of their reward structure you'll see that you require up to 1,000,000 PPO coins to be able to double up for the last block, this sorta leans towards the devs knowing the coin may in fact be worth way less towards the end, meaning 1,000,000 PPO coins may only be worth 3-4K.
This is of course my observation only, like I said I still dont think its a scam ya just gotta be clever with this one!