Any breeder who violates the YTCA's Code of Conduct and tries to sell you a puppy before it is twelve weeks old is not a reputable breeder.
8) All puppies leaving the breeders possession will be a minimum of twelve (12) weeks
of age to facilitate adequate socialization as well as appropriate emotional and
temperament development through interaction with siblings, dam and other dogs.
There is also much information supporting keeping toy breed puppies until they are 12 weeks old:
Professional Dog Trainer Melanie Schlaginhaufen -
http://www.knowingdogs.com/Images/Ch...our_Family.pdf (see #8)
Small Dogs, Big Hearts By Darlene Arden an internationally recognized authority on Toy dogs and their care, and a Certified Animal Behavior Consultant.
(see page 15)
http://books.google.com/books?id=P9n...esult#PPA40,M1
A Good Breeder by TD Yandt a noted animal trainer
noselicks.com - Articles - A Good Breeder
CanineDimensions.com, Dog Obedience Training, Dog Training Specialists
CanineDimensions.com, Dog Obedience Training, Dog Training Specialists (see #9)