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 attacking the villagers at night. Usually, a whole pack will concentrate on one door or villager. Villager breeding will keep the population up. As of 12w08a, villagers have Iron Golems to defend them. Until now, only this was added, but there may be more features in future updates.

Trivia

 * When a zombie is attacking a villager or door, it usually cannot detect you unless you attack him.
 * Zombies also attack baby villagers.