I think there is a huge difference between a 3 lb. dog and a 5lb. dog. I will still love my dog if she ends up being 5lbs. and I will still consider her a small dog BUT I won't be able to include her as much. (I don't want to start another debate, I am just stating my reality) I REALLY want my dog to be between 3 and 4 lbs. Tiny (under 2lbs. would be too much work and not seem doglike to me)
You CAN find a healthy tiny, it just takes a lot of time and research. Not all people that say they have tiny dogs are considering their health and not all of them are honest. (Beware of Tiny
skinny dogs posed in/as teacups)
There was a discussion about this last month. Read how others found their dogs.
http://www.yorkietalk.com/forums/showthread.php?t=9159
good luck and let us know how you are doing with your search.