Useful information, certainly. But only in desperate circumstances. If you have a genuine need, okay, but have no doubt that there is a degree of cruelty involved.
I'm pretty sure that this is highly illegal (and more broadly, grossly unethical) in a great many jurisdictions. I think it extremely unlikely that responsible trappers would use this sort of technique, at least for commercial harvest.
/okay, end rant
How long have you been trapping?