He's just telling that if ever that you will invest with some sites with ponzi scheme, make sure that you would withdraw your money in an instant whenever you get your money back. But I am a little bit confused because some of these sites never let us withdraw the money that we deposited. Most of them doubled the required money needed to deposit in order for you to have a successful withdrawal. And I agree with you about avoiding these sites incase you notice that there is something wrong or bad reviews about it.