My own experience (from before I knew any better) is that commonly sized "breeder boxes", "breeder nets", etc., do have a detrimental effect on the fish (most of my livebearer experience is with guppies), especially if used bare and in a tank containing other fish. Specifically, what I observed was that in these boxes fewer fry were born, the number of miscarried fry (or dropped eggs) was higher, the birthing date was noticeably often later than expected and a higher proportion of females died during birthing. There were significant differences even between a "breeder box" in a reasonably planted tank and a bare 5 gallon tank. This is based on my observations from a few 1000 birthings and I have always tried to keep written records of all of my breeding attempts.
On the other hand, I do expect that a 2 ft net is considerably less likely to cause a problem for the fish compared to a (for example, measuring the only one I can find left over from those days) a 5*3*3 inch one.
As for commercial breeding, I don't think it is particularly relevant to what *we* do at home. After all, many commercially bred pedigree cats and dogs are kept in small cages, and I don't see how that could ever be of any good for the animal even if they regularly give birth and I feel the same about fish. Most of us are not in this for the money, why should we not try to be better?
I hate to inhibit the free flow of information but will start trimming threads if this disrespect for other people's breeding methods continues.
What do you consider disrespect? Advice and recommendations based on our experience and/or observation? Opinions do differ: if no one is able to disagree, then there is no point for a forum! Might as well just write up an FAQ based on an individual's opinions.

And what about my breeding methods? If you tell me that what I have found to be true is not, you're disrespecting them yourself
