The purpose of this group is to allow good Left 4 Dead players to find other good players. Good players know how important a good team is for having fun in L4D. Members of this group were invited because:

-They communicate well during games. (Using text or mic)
-They play well during games.
-They don't act stupid.

Those are the only requirements. This is not a clan, just a group to make it easy to find good players to play with.

If you play a really good game with a group of people, invite them! Other players want to share the fun and excitement of playing with a great group of people.
This group also removes the need to add a bunch of strangers to your friends.

:)