You most definitely need to know about the Mavrodi Mondial Movement (MMM) which has been quite a problem in Nigeria, there is a Wikipedia entry about it and the description is that it’s a ponzi scheme out to prey on mostly the poor. How it works is that you give them money with the promise that it will be multiplied by the thousands. Naturally, it starts with cautious people who put in small monies, like Kshs 500-1000 ($5-$10) and when they get the money multiplied by the thousands, they get greedy.
What happens after is they put in much more money, probably tens of thousands in the hope of becoming millionaires. They also sell the idea to friends, family and fools. Then the pyramid scheme architects disappear as quietly as they came. And we have people crying all over, probably very much in debt and overdue bills, asking for the government to assist them get their money back.
This is supposed to be illegal, and we are being warned. Warn your people.