Err... not sure I see this a simple "yes" or "no" question.
I think, with a game as popular and new as L4D is, it'd be good for us to have some presence there. Not only would it help keep members of eGO together, but it would allow us to continue to to show potential recruits (as well as sponsors) that we are a community that keeps up with the latest games.
I'd be for forums and a Steam group (so people can discuss the game and create matches), but no official servers. L4D is set up so a lot of people can set up their own servers. Perhaps we could have something like AR where a few eGOs can run servers with pubs and try to recruit. Make it a mini-division where we can still accomplish some of the goals of eGO, but something that does not require the financial support and active leadership of our other divisions.
Sadly, I don't think L4D is set up well for our admin structure, and to be frank, it is not a game I would admin as I really can't see myself playing with people who aren't my friends. I am sure I am not alone in that. But, I still think we can manage to get eGO involved in the game provided we are willing to approach it from a different angle.