I grew up with cats and ours never wore collars. When I got my own, I thought I was being responsible giving them reflective safety collars with name and address tags attached. I was super careful: they only ever had the snap-open safety collars and I was very careful about them being correctly adjusted.
Molly was forever losing hers, and one day a kindly neighbor returned one to me. She had also written me a letter to warn me about the dangers of collars on cats. I thanked her but reassured her mine only had "safe" collars.
Shortly after the lady with the letter, Mable was grooming herself one night when she suddenly froze. I could see something was terribly wrong and as I got closer to her, I saw her mouth was wide open and her tongue was turning blue rapidly. I had no time to get her to a vet. She started to "scream" and tremble and I then saw her jaw was wedged tight under her collar and the position of the safety buckle meant it was not going to open. By some miracle, I managed to hold her still and was able to cut the collar off. She was fine. I was not! It was a truly terrifying experience and I am certain she would not have survived if I had not been there. I can only assume her airway and blood flow was being restricted. Molly's collar was removed immediately and I have never and will never put a collar on a cat again.
I have heard some terrible horror stories of cats and collars. By nature, they are so different to dogs with their leaping and climbing, although in this case Mable was simply grooming herself. The anatomy of a cat is also different with a much shorter snout, and I urge all cat owners to have their cats micro-chipped and not to take the risk of putting collars on their cats.