All I can say is that the victim of this such a ponzi are just greedy, lack information, lack knowledge and need experience. But in this matter, I think experience is not that needed because it is not possible to earn such a great amount within such short period of time, but what can lure greedy people, even if I do not know it to be ponzi, I will know it is definitely a ponzi and should be avoided.
They really are, but we have to keep in mind that greed stems from the lack of information and experience from scams. You will be able to spot Ponzi schemes if you just ask the right question and you think that they can't answer it then the chances are high that they are a scam.