If you go to an event and the organizer doesn't show up, try contacting the organizer to find out what happened.
If you find yourself a member of an inactive group, you've got a couple of options.
If you're on the group's leadership team, you may be able to rally other members to schedule an event on your own. You may be able to start a new thread on the group's message board, or send a message to the group's mailing list.
In some cases, if you're not able to get in touch with the organizer and you feel they aren't organizing the kind of group you want to be a part of, your best bet might be to join a different group.
Or if you're up for it, you can start your very own group and invite others to join it.