I keep native species over here in the UK, and it's amazing how few people do it. (Alot think its illegal...which I suppose is a good thing)
although we have very few species compared to the states, so im sure that has something to do with it.

The only reason I would remove a juvi/adult amphibian is if it was in need of help, couldn't properly fend for itself (injury/deformity) or was an albino which would be much more likely to be eaten by a predator.

The main reason for my current collection is due to raising some spawn which I thought would be nice for my little bro to learn about etc.
Unfortunately, I didn't have any proper info regarding supplements and lighting etc and many of them developed MBD and died. This is what brought me onto forums tryig to find out how to help etc... and luckily I still have two remaining toads who are now over 3 yrs old.
After learning more and more, and being more confident, I collected some frogspawn, and raised 3 frogs to adulthood. They bred last year, so I raised the tadpoles until close to metamorphosis, then released most but kept a few back. This year the adult trio bred again, so i'm partially raising the tadpoles, and once the weather settles down, EVERYTHING will be released back into the wild. (the adult trio, the 6 juvies and the tadpoles)

I have a MFF trio of common toads and next year intend to try & breed those, and if successfull will release the offspring (except a couple)