I found this question on Quora.

MLM means Multi-Level Marketing. Some popular examples are Amway and Herbalife. These businesses are in some degree similar to a pyramid scheme, though the difference is real and MLM members will gladly tell you why. In these systems, each member has the job of selling a product and also recruiting new members who will route some of their revenue to the recruiter.

My answer:

There are a lot of reasons why MLM’s are a scam, but the one that scares me the most is the answers you get from MLM’s when you ask for some evidence to show how many of their members actually succeed.

If you can get a number at all, it’ll be very low and it’ll probably be accompanied by excuses that blame the members for not being committed enough. Whether that’s true or not, it doesn’t seem to matter enough for the MLM’s to fix that problem.

They’re happy to take your money even if you’re extremely likely to fail. And that’s why it’s a scam.