People have been blowing up villages since Minecraft 1.8 came along (before villagers were added), and merciless killing has continued ever since. But in Minecraft 1.4, Jens has revealed that killing villagers could have bad results. "Used to kill villagers because you don't like what they offer? Well, in the future you will have to face the consequences of your actions," Jens said in a tweet. This is a bit vague at the moment, but more details should emerge when the first 1.4 snapshot gets out. In Soviet Russia, villagers kill you.
Source: @jens_