I never have collars on my dogs, especially in the house.

My aunt's dog got her collar stuck on a drawer handle once. She panicked and pulled the drawer out of the dresser and it clunked behind her and she panicked more and drug it through the house. She was so scared she peed everywhere and emptied her anal glands.

I was also at a dog park once when I saw two dogs playing by grabing each other's necks etc. Well one dog got it's jaw stuck in the other's collar. It panicked and tried pulling away, but it couldn't get free. The other dog started to panic as well. It almost turned into a fight, but the owners were quick to help them get unstuck.

I don't think collars are necessary in the house, unless of course you have dogs that bolt out the door.