Agreed, they are def not for homes w/ children, clumsy people, or big dogs. They shouldn't be allowed to jump up and down from things, they are very sensitive to cold & can develop severe upper respiratory infections. Also with any small breed, especially the tiny ones they're blood sugar goes up and down so quickly they can go into what I call a "sugar fit" when they burn to much energy w/ out eating, so they do need to have access to food pretty much constantly especially when they are puppies to avoid this.
I have a 2.5 lb chihuahua, and she has lead a pretty sheltered life, she can't do alot of the things other dogs can do. I got her from a breeder and I didn't anticipate her being so tiny, I did want the smallest one in the litter though and that is most certainly what I got.. She has regular vet check ups (at least bi-montly) and fortunately she has had no problems and is very healthy. Any breeder or store that refers to their small dogs as teacups is one to avoid.