Zombie siege

Sieges are an upcoming feature in Minecraft. The first part of the project was added in 12w07a. Currently, zombies have a chance of coming in to the village in packs and attack the villagers at night. Usually, a whole pack will concentrate on one door or villager. Villager breeding will keep the population up. In the near future, villagers will have a way of defending themselves.

Currently if a zombie is attacking a villager's home, it will not be able to "see" you unless you get very close to it. Instead, it will remain trying to break down the door to get to the villagers inside.