there is 1 thing you can do about this and that is to not keep the game up to date.
right click on the l4d2 line in the my game tab of your steam client and choose options in de menu, now go to the updates tab and select do not automatically update this game.
now click close and it will not update the game anymore.
I believe Rickmon said
[Edited by NobleCrusader, 12/19/2009 3:16:49 AM]
Uhmm