I've worked in the past with company which used MLM, but for my experience, in the most case, there were only ponzi-scheme company hided by MLM marketing.
You can compare gambling with HYIP, this is true, but the real MLM is really another kind of thing and shouldn't never compared to gambling.
Maybe gambling can almost be likened to an HYIP because we both deposit a certain amount of money and then we just have to wait for the time limit we can take the profits.
What makes HYIPs almost the same as gambling is that no one knows when the HYIP company can go online and that can make us worry if the HYIP company closes before we can take our profits and capital.
But if we say gambling is the same as MLM, then that's not quite right because MLM can still provide benefits in recruiting new members.
It's just an obscure MLM program that we might equate to gambling.