Personally, I don't like them. If the dog isn't a hunting dog, and isn't going to be running around in heavy brush day in and day out, I see no point. For hunting dogs, I can see why a docked tail and cropped ears would help, so they wouldn't get so beat up, but other than that, I am VERY much against them.
I will exercize my right as a vet to refuse to crop and dock.
And Gingerrr... for dogs... I don't think a rubber band would be very humane, and I think that if done, it has to be for a good reason, and humanely done at the right age, but did you know that they use rubber bands on sheep tails? That's how they dock them. It's painless for the lamb, and the tail eventually falls off. Sheep don't naturally have ultra short tails... they actually have very long ones.
But back to the subject of dogs, no, I do not agree with cropping or docking. I've seen rottweilers, dobermans, corgis, and other dogs without, and they're BEAUTIFUL. They're natural, happy, and you don't see them trying to wag their whole butt when wagging their tail (not that that happens with all of them).
Also, if not done properly, the dog can end up with SERIOUS problems later on. Infections, bone and tissue left over that causes more infections and problems... etc.
So... if you want it done, make CERTAIN that the vet is QUALIFIED, has done it many times with absolutely ZERO to very little side effects on any of it, and so on. I'm against it... but if someone wants it, it needs to be done RIGHT.
Dumas... unless the dog is extremely active (like... needs 5+ hours of almost non-stop running a day), or their in a dangerous home setting (e.g. heavy things that could fall at any time, construction, huge things that could easily fall), it is pretty uncommon for any dog to break it's tail. Sure... it happens, but it's uncommon. We've owned about 20+ dogs, and none have broken any tails, or even gotten close to doing so. All of our friends have had dogs too, same went for them. It's uncommon for a dog to just break it's tail. When something scares a dog, it's tail is not out in the open, it immidiately goes between its legs. Most dogs only carry their tail in a relaxed, down by the legs position anyways, except when greeting, acting dominant, and so on. If the dog carries it higher, there are usually only a few reasons: the dog is bred that way (Shar Peis, Papillons, Keeshonds, etc), or the dog has some slight deformity with it's back and tail.
Sure... when a dog is laying down, usually the tail is out. But unless people drop things on the tail, or step on the tail, the dog is safe from harm's way. So, for the most part, it's uncommon for a dog to break it's tail, whether it's full grown or puppy. Yes, it happens, but not as often as you're making it out to be. :)