There is an export feature, which I just did as a backup for my groups: Add: 'members/?op=csv' to your group root, and you should get a CSV dump of your member

There is an export feature, which I just did as a backup for my groups: Add: 'members/?op=csv' to your group root, and you should get a CSV dump of your members (most of what's worth backing up): meetup.com/YourCoolMeetup/members/?op=csv