Mark people as a no-show if they change their response to 'No' after the RSVPs have closed.
Right now, people cancel at the very last second and are not held accountable for messing up plans or reservations. They should take a hit of some sort for this behavior. If my RSVP is closed it's because I need a firm count by that date/time. These last minute cancellations really screw me up.
A top rated Meetup Organizer commented
Emily Post says a last minute cancel IS a no show