Recently Lifehacker posted an article about cognitive biases that lead to bad money decisions. They are, obviously, perfect described the mindset of an MLMer. Indeed, MLMskeptic here has covered most of them.
Sunk-Cost Fallacy -- if you have put money and effort in, you would not want to give up. This is also related to "Ikea Effect".
Choice-Supportive Bias -- also known as post-hoc rationalization, you made an impulsive decision NOT supported by logic, and later you tried to come up with reasons why you made that impulsive decision. You will even rewrite your history and memory to somehow "prove" that you made the right decisions.
Anchoring Bias -- you rely too heavily on the FIRST piece of information and let that information affect your subsequent decisions, even of that first info is outrageous or wrong. Even when you are shown proof that the initial information is wrong, you fail to correct yourself and your thought process.
Bandwagon Effect -- "everybody else did it" somehow proves that it's logical, even when scams can have millions of victims. Popularity does not prove veracity or truth.
Status Quo Bias -- If you prefer the things the way they are, even though it's bad for you, you're definitely affected. Scam victims often refuse to take action to protect themselves because they believe they cannot be in a scam, and they want to "wait things out" even as the scam continue to take their money and provide one excuse after another.
But go read that article.