A Ponzi Scheme, named after Charles Ponzi, is a strategy that con artists use to steal money from people. In a Ponzi Scheme, the con artist takes investment money from one person and lends it to another without any real investment.
" The rob Peter to pay Paul principle "
Madoff was able to keep it going because more new investors kept coming in, and while he does need to pay the old investors that wanted their money back, he got more money than he needed to pay them. He was able to always attract enough new investors, so he always had the money to pay back.
According to the video, people who are Ponzi Schemers usually have a very friendly and opening personality. Very inviting and charming. This is because if you are friendly and nice, you are able to attract more and more people since they can trust you.
Madoff even came to people's funerals and weddings. If he was invited, he would be there. That should tell you what type of person he seemed like he was. (Indirectly quoted from "Scamming of America")