By my count it's actually 13. I'm going through BoardingArea (I wasn't part of the 20), and stimpy isn't on the flight. There's a few reasons we don't know the other seven, IMO:
1. Maybe they're very infrequent posters (possibly even have zero posts), and just saw the announcement and sent an email. They might not even know about CommunityBuzz.
2. Maybe the offer was for 20 people, but that was already accounting for the expected buffer of no shows, so it's actually less in the end.
3. Maybe some don't like some of the rudeness in the other thread and don't feel like responding, which quite frankly I can't blame them for.