about those zombies...

[Grand_Pamplemousse]

No they don't. This is made quite clear by Max Brooks. The moan may appear to be some form of communication, but in reality, it's just a reflex. They moan when they see a meal. Basically, the other zombies respond to sound, so the moan attracts them. Basically it's an accidental dinner bell.

Sometimes the reflex can call zeds from about a mile around. If lots of Zeds are in a concentrated area the moan can attract zombies from hundreds of miles around leading to situations like the battle of Hope, when thousands of Zeds were called in from the surrounding area. Then another 10,000 from the next area.

Damn, I read too much zombie fiction.

EDIT: @Tharwen the bile is actually just pheromones, or something. Apparently it reacts with the human skin to attract the zombies (as in it doesn't attract any zombies to the floor if you bile on the floor. Also Bill in the beginning video touches some of the bile causing a rush of zombies to come soon after).