MLMs can be actually viable jobs for a very select few of people. Not entirely unlike how you can theoretically make money at a casino. There need to be winners to the game once in a while, or else no one would play. The game is just rigged wildly out of your favor.
The general structure of an MLM as I understand it is sort of a cross between a wholesale job and playing a mobile gacha game. Unlike a normal business where you purchase stock to match your demand, and only stock items that actually sell, an MLM contractually obligates you to buy a certain volume of stock, and each shipment is essentially a lootbox full of who knows what. It then becomes your responsibility to get rid of the stock any way you possibly can.
When you buy all that stock, you are not buying it from a factory or a warehouse. You are buying it from another person in the same position as you, one layer up. They are also playing the lootbox gacha and trying to get rid of all the crap. Except, hmm, now they have at least one person beneath them who is contractually forced to buy from them, and can't select which stock they're buying. Gee, I wonder what you're gonna be getting...
Whenever you actually do manage to sell something off, a cut of that kicks back to the person who sold you that stock. And a piece of that kickback goes to the person who sold them that stock, and so on, up and up.
The real money in MLMs is having so many people beneath you that the kickbacks start adding up into significant income. This is theoretically achievable. But it requires a very specific kind of personality matrix who is not squeamish about being a little cut-throat to get ahead, and generally requires a significant investment where you are going deep into the red just for the opportunity. And even if you do make it there, you have to accept the knowledge that your profitability can only exist necessarily because of the existence of many people beneath you all spinning those slots and losing the rigged game to the house (who by this point is you).
Had a lapse of judgement once and sent one of those 2FA passcodes sent to me via SMS to a shady guy on Craigslist. This was back when 2FA was still in the process of becoming ubiquitous, I do not believe I had seen one before that point.
I believe the only thing it allowed them to do was register a Google Talk number in my account's name. I immediately dissociated my account from the number after this interaction (strangely, you could not actually cancel the number, only disown it, so I guess the scammer still got what they wanted anyway) and changed my account password for good measure.
I've also bought many bootleg collectors items off of Ebay. Though, each time I've done so was fully knowing the listings were lying, and still wanting the bootleg garbage anyway.