You don't have access to the e-mail addresses for your meetup group members so it's difficult to move to a new service. I think this analysis ignored the switch

You don't have access to the e-mail addresses for your meetup group members so it's difficult to move to a new service. I think this analysis ignored the switching costs issues and the fact that it's still free for attendees. The second point means that there is a large group that is notified when you launch a new group and they have no incentive to switch to a new system.