I used to spend a lot of my life playing Counter-Strike:Source - in particular playing a modification for the game called Zombie Mod.
I thought I'd try and play it again today, and I can't believe that people actually play it - let alone that fact that I used to. Note that on the second round we won because someone threw a grenade at a zombie, and it got stuck in a drinks machine.
It really annoys me that mods like this can still be played - even though they were quite evidentially coded as some kind of a test that was just thrown together and released. That's me being critical of the maps too - this map is one I remember from when I used to play the game some years ago.
I don't think the the Left 4 Dead team have anything worry about...