Napoleon Hill's works "The Law of Success", "Think and Grow Rich, and the concept of Mastermind has been around for decades. For Mastermind to be successful the participants must come together in a spirit of harmony and good will, genuinely wanting the other people to have their goals, dreams and desires manifest in their lives. It isn't about what's in it for me. If you are not focused on assisting the other person in your Mastermind to realize what s/he wants, then the power that Hill is referencing is lost.
Trust comes into play here. We need to trust that if we are truly committed to the success of the other people, our success is ensured. So, being involved with other people you intuitively know will hold your Intentions on your behalf is important. You can be successful without that support, but when you have it everything works more effortlessly.
Have you belonged to a Mastermind? What were/are your experiences?