Meetup, like Facebook, is an online social network; however that is where the similarity ends. If you have ever tried to organise an event through Facebook you will know that it is unreliable and unrealistic. Yes, your Facebook peeps will join your event; however, as you know it is a heartbreaking exercise as you stand there at your venue with half a dozen people even though 80 people RSVPd.
Meetup is different. Meetup is purely for running events. You know that the people who are on the Meetup site are looking to attend an event and are not going to get sidetracked.
I've included the name of my group as I will be using screen shots from my group in my diagrams.
Over the last 10 years, I have watched Meetup go from a free site to a monetised site, where the person who starts the group (The Organiser) pays a yearly subscription.
This subscription is very reasonable and can be raised simply by asking for a small donation from your members at any event. The one thing that thankfully has not changed is that Members don't pay to join groups, hallelujah!