Multi-Level Marketing, e.g. that person from grade school who messages you out of the blue to ask how you're doing, and then tell you how much better you'd be doing with daily injections of IsoLeanIonigenTonicWater which you will also want to sell once you feel amazing/thin/virle/whatever.
I used to program in a co-working space for fun where the company next to me was trying to build one of those schemes with some sort of ionized water. The CEO was perpetually convinced that if he "just got 400,000$ in funding" everything was going to be great. All the employees seemed to hate it there. Was pretty annoying to listen to, but not as annoying as the guy a few cubicles away who was trying to sell gold.