For those of you wondering what I was talking about with generator-camping — that's exactly what's going on in this clip.
The level is set in an abandoned motel and the generator is in the drained pool at the center of the complex. Now these Infected are mostly just mobbing the back right hand side of the pool where the ammo and health items are. But at about the 26 second mark, you can see green acid and fire just covering the generator area while some poor sap gets hauled off by a Smoker.
See? Generator-camping!
Video Games | Left 4 Dead 2 | PC Infected Gameplay