[Wrath]

It's called docking and it's part of the breed standard. Traditionally, a lot of working breed and sporting breed dogs have their tails docked. One of the reasons I've read is that it is less likely to get caught on something or bang in to something and suffer serious injury for such active dogs. I've also read that dogs used for protection have docked tails to give wrong-doers less places to grab.

It's becoming less prevelant of a practice, a lot of European countries have banned docking and even in the states there are a lot of people who are against it as well. The AKC standard still calls for a docked tail, so having an undocked Rottweiler would prevent you from competing in conformation, but that's really about all. Some people like the docked look, some people like tails...