Short version (IMHO) is that Masterminds are excellent when you get good people (seniority, experience, entrepreneurial spirit etc) and they are far less good with less relevant people.
Take a bunch of very early stage peers. They often have more limited and similar knowledge and networks. On the other hand, take a bunch of essentially lonely and talented entrepreneurs and stick them in a room, magic will happen!
I reckon it's some combination of neglectedness/isolatedness and relative value.
I'm a member of a Mastermind group (from a... (read more)