While registration for Geek Nights is intentionally loose (low process) there is a practical limit that the ThoughtWorks office space we use can only really take an audience of 40 people. Any more than this and people cannot see or hear the speakers or presentations.

Therefore we use Upcoming to manage our attendance. The Upcoming page is linked to from each event page in the wiki. Once the Upcoming guest list is full then we cannot accept any more visitors and you're out of luck.

As Upcoming requires a Yahoo Id we will also accept someone signing up to an event by saying so on a comment thread on the event page.

If we ever needed to chuck people out of an event we would use the Upcoming List and Wiki page to determine who had signed up and bounce everyone else.