Cropping no, because it's purely aesthetic, docking I'm okay with as long as it's not done purely for aesthetic purposes. Mlogan brings up a good point with breeds that have powerful tails that can self-injure, but beyond that there are reasons why working dogs should have their tails docked.
Take your doberman example for instance, what job does a dobermann pincher generally hold in the dog workforce? They're one of the most popular breeds to have as guard dogs due to their tenacious and territorial nature combined with an impressive sprinting speed, endurance and their generally above average intellect. Now look at your two dobermann pics and tell me which one looks the most intimidating. That's a slight acknowledgement to why the breed is cropped, I understand it but making the dog more intimidating is still purely aesthetic and I'm still against that (plus I'm kind of a sucker for floppy-eared dogs), but can acknowledge that I understand to underlying logic to doing so in some cases.
The purpose of docking the tail however, should be obvious in light of the dog's career. As a guard dog or hunting dog a long tail can be a liability that trespassers/prey can latch onto when cornered and use to control and hurt the dog. Furthermore there is a strong chance that a guard dog will be working around an area enclosed in barbed wire that a tail could also get caught on (one of my dogs got theirs caught on a wire before just by walking beside it and wagging, it isn't a pretty sight) and the same can be said for dogs that herd livestock. Tradition also dictates that farm dog's tails are docked because they can be stepped on by horses and cows and such but I personally find that unlikely and tend to feel that their proximity towards wire fences that can and do ensnare dog's tails and injure them is likely the sole reason for the tradition among farm breeds.
So yeah for the 5/6 of us so far that are arbitrarily against both practices might help you to research the reason the practice came into existence first. While it is true that both are done purely aesthetically at times it's also true that it is frequently done in certain specialized breeds for the dog's own well-being in preparing them for the career position they will grow up to fill. You can get all PETA about that too and bemoan a dog's lack of choice in the matter or you can take pride as a dog lover in the knowledge that dogs are one of the few animals intelligent and driven enough to serve a purpose for humans beyond just simple pets and often hold careers that are more beneficial to society than a large portion of human careers are. I've helped train dogs before, some of them are awesome, brilliant creatures if given the opportunity to grow their talents correctly. Anything we can do to make a dog on the job safer I find admirable.
Also I saved this for last for a reason but is docking a tail really any different to what most of our society (73% of world population as of shoddy 2010 google statistics) does to male babies in order to 'protect' them from urinary tract infections as they get older? I mean if we aren't traumatized by that practice (and I know no one whose ever claimed to remember it) then what exactly makes you think a puppy who lost his tail before he learned how to open his eyes is even going to remember he ever had one? Not even saying that makes it right, what I am saying is that we regularly perform a similar procedure on half of our own population, yet I've never really seen a moral discussion about doing it to a baby human and this is at least the third discussion I've been in about the ethics of docking a dog's tail. Just food for thought.
