The family that introduced me to the church also introduced me to an MLM.
I signed up when I was 18 because I thought I could make it big - got a credit card and put a few thousand on it. Even spent $$ on going to some trainings where all the big wigs drove up in nice cars and people shared their testimonies of how their lives had changed because of the products and business opportunity. I bought in to all of it.
Luckily I lived and learned, and was able to pay off all of the debt I accumulated 6 months after getting married, but I put off college to work and pay it off. It all worked out in the end, but I have a pretty sour disposition to MLMs due to this experience. And I absolutely hate it when people use anything related to the church to make connections or pitch MLMs.
Personally, I think the church needs to warm people to stay away from MLMs in their self reliance classes. Join if you like the products and want a discount, but it's not a legitimate business opportunity.