Who organizes these things and who shows up?

A M&G is a 'happy hour' event where hobbyists and providers are invited to meet each other in a social atmosphere. Different regions of the country have different rules, etc. but I think they are all pretty much the same. In my area they are organized by several hobbyists and providers, we actually have a committee. Everyone is strictly screened - all providers must have a website and reviews, all hobbyists must have reviews and a presence on the boards. It is actually a fun time to meet others in a no pressure atmosphere - strictly a M&G - nothing else happens there.

Either a group of local providers or a well established business, tied to the hobby.
In Chicago, we have to meet and greet forums, one that is hosted by the ladies, and another that is hosted by Provider Video.
Strictly a party event, held so clients can get to know the ladies prior to actually scheduling a session with them...