I have a tiny too. He lives with me half the time and with my parents half the time. His name's Kasey, as of 3 days ago he weighed 2 lb 2oz, per vet scale. Want to know why he was at the vet and on the scale? Because he stumbled and fell on
ONE stair...the 'step down' into my parents' den, less than a foot tall, and it knocked him out cold....when he DID get up, he was shaking uncontrollably. Would that have happened with Abby, who's 5 pounds, or Cody who's 6 or Trixie who's 7? Probably not. Health wise Kasey is strong as an ox...no problems at all there. His parents were 5 and 5 1/2 pounds. His littermates are around that size as well. He isn't so big, but I would give ANYTHING if he were.
Health wise there may NOT be anything wrong with a tiny, but environmentally, it's dangerous...why would you TRY to produce one that small. It's not a matter of, "oh, you just have to be careful". He's no bigger than a sneeze and he ACTS like a big dog, but he's not....he's fragile, period. Why wouldn't you want to try to avoid that?