Let me start off by saying I've got absolutely no issue with people doing this especially if you tag them and check on them.
What I absolutely despise are the pieces of trash who set them out and don't ever go and check on them again. I have a huge problem limb lines here in central-ish region of Kentucky.
I personally cut down nearly 50 limb lines last week and rescued a cat fish from one while smallie fishing. Why? For starters they weren't labeled, thus making them illegal. More importantly we're in a huge drought right now and the river I go to a lot has dropped almost a foot in the past few weeks. All these lines where hanging out of the water and were in there long enough that you could see the original waterline on them, not to mention none of them had bait on still. One even had a small catfish that partially out of the water even. Judging by the hook wound I'd say it'd been on there AT LEAST a full week. It was already starting to scar over...
Point being, CHECK YOUR LINES AND DON'T JUST ABANDON THEM. Take them back out of the water when you're done. I understand jugs might go missing if the fish travels far enough, but limb lines aren't going anywhere. Don't leave all that string and hooks lying around all along the banks of rivers. If you aren't responsible enough to check on them then don't use them. Simple as that.