I used collars only for walks, but after reading here, I will soon be switching over to harnesses. I never leave anything on my pets when I leave them unattended in the house. Heck, they get tangled up in underware!
Think of it like this....if you can imagine what "could" possibly go wrong, then it "can" go wrong. And that pretty much goes for anything around your house. There are many stories here to prove this. Not all accidents can be prevented, I am not saying that at all we just do our best to prevent them and coming here to ask questions and learn is a great way to start!