I'll say that I would never breed a girl in the 3 pound range. It's just not safe IMO. I have a wonderful little girl with a divine personality that I bought to breed and so wanted to as she grew to be more beautiful than my expectations. However, by one year old she had only reached 3 pounds and I did (what I consider) the responsible thing and had her spayed.
I suppose breeding tinies can be done but I really don't see the point. Someone used the analogy of hamsters and mice breeding safely. While that's true, they are kept in a cage. They are in no way a companion pet. A dog, IMO, needs to be large enough to have a reasonable chance of making it through life without a simple mis-step being a tragedy.
Right now I have a little girl that is 7 months old and weighs 2 1/2 pounds. She was bred from my 3 pound male and a 5 1/2 pound girl. She is just now getting to the point where I feel safe in allowing her to go to a permanent home. She is so small and I worry about her so much. It's not that she's not healthy, it's the risk of injury.
I guess that's where my problem would be in someone breeding for not just tinies...but ultra-tinies. How could any breeder feel like they could find so many truly qualified homes for such little ones? I would wonder how many really make it to a ripe old age as they should? Good homes for tinies are very hard to find and, for this reason, I think that breeding for them is wrong. It may not be so much as CAN you breed them but SHOULD you?
The OP is only asking the obvious questions. If someone came to the breeders' forum and asked the breeders to check out a site they were considering getting a pup from where someone was breeding too-small girls, it's a no-brainer what the response would be. Or should I say what the response HAS been as just this question has been asked many times before. Typical responses would include words like...'irresponsible', 'unethical', 'greeder', etc. and you would see plenty of these...
To see this type of breeding program being embraced by some has got to be confusing to newbies and long-time members alike. I am personally distressed by it as this can only lead to stoking the demand for these ultra-tinies. It's something I thought I'd never see here on YorkieTalk (shakes head in disbelief).