On Tail docking, one place is here:
YorkieInfoCenter | Yorkshire Terrier Tail Docking
Primarily docking tails are done because the AKC requires this for show dogs, as do several others. An interesting point is that the United Kingdom does not recommend this:
Anti-Docking Alliance Web Site
There is also an adorable video here:
Why Yorkies Should Not Get Their Tails Docked
and a real great article here:
Dog Tail Docking: Issues and Health Implications of Docking, whether on a Boxer or a Puppy
I really though long and hard on this issue. I have nothing against those who do or sell their pups and command the high price for registry, or because of being a show quality breeder. I did show my dogs many years ago, have always had AKC as well, but I love their tails and know they are as adorable as Yorkies who don't have tails.