We were taught to write negative reviews on these kinds of schemes on a blogging course I took. It's a good way to bring attention to a legitimate project. Show the Ponzi then show a much better and safer option.

You could include an affiliate link after your warning and people will still sign up for the scam. Is that immoral? Idk. They're bent on throwing money away. I would put that money to better use than the ones running the scam in most cases. But to earn off friends, classmates, or family is taking it too far. They'll come back and blame you even though you warned them. Not smart.