I'm going to give my 2 cents worth. I got my first yorkie at one day shy of 7 weeks, she was eating well and very healthy, never had any problems with her. The socializing, oh my, all I can say is she's probably been the best dog I've ever had as far as never biting at my fingers. My old vet will tell you 8-10 weeks is the best time for a pup to go to it's never family so they can start bonding with it. I'm not going to say whos right and whos wrong, because I think everyone has a good point, but, I can honestly say the ones I have gotten younger, have been much easier for me to work with on training. Maybe the question should be who got their yorkies at 12 weeks or later and has had problems still with biting, housebreaking, etc. Everyone needs to take a "chill" pill.
Remember, everyone is entitled to their own opinions. Not one person is right nor wrong when it's their opinion