I had some colleagues who got involved into those pyramid scheme. As in this case, I was surprised because they were not uneducated people. Most of them had a university degree. Most of them moved by greed, albeit with an annual income not high as a doctor.
I was very surprised when I found what was happening, because a pair attempted to recruit other people at the office. When I gave a look into what it was, I smelled a fraud immediately - it was so blatant! I called them into my office, and asked if they understood it was a fraud - which they denied vehemently.
I told them they were free to lose their own money, but to keep that fully out of the office, don't try to promote and recruit anyone there, and don't use any of the company devices - or any connection to the company, for the matter - for anything related to Telexfree. They answered I had not the authority, I replied we could have it escalated to HR if they wished, and that was enough.
Not long after the pyramid started to crumble. I don't know how much they gained or lost, and how many other people they deceived. None of them ever told me I was right - don't know, maybe some even hoped to make some quick bucks more before the fall...