That cool intro to Left 4 Dead isn't just for kicks. It's the game's version of a tutorial. From a blog entry by Valve's Jason Mitchell:

We decided that it would make sense to begin the game experience with a non-interactive introductory movie that could get players revved up and subtly cue them to important gameplay mechanics such as "light disturbs the witch" and "car alarms attract the horde."

Mitchell also shows some early cuts of the cinematic, back when Francis was more burly and hirsute, apparently played by an unshowered Gerard Depardieu, which made his flirting with Zoey even more creepy. Thankfully, Francis slimmed down, got a shave and haircut, and realized that Zoey was out of his league.

Mitchell discusses some early snags with Zoey appearing weak and the hunter pounce being inadvertently funny. He even gets into this level of detail:

The emotional beat between the grenade explosion and the arrival of the helicopter was breaking the otherwise quickening pace of the piece and so it was cut. Although this was painful because it removed an opportunity to further flesh out the characters, we felt it was the right move to cut this moment to keep the pace up.

Now that's director's commentary.

On a related note, watch writer Chet Faliszek interviewed within the game by someone at MSNBC who thinks Chet's name is "Ted", despite the word "Chet" hovering over his head. Well, over Zoey's head. As Faliszek explains:

I'm playing Zoey. I've got moxie and sass, just like her.