Are there any dangers that a user of retractable leashes should know about that don't involve misuse by the owner and/or can't be prevented by responsible owner use?
I've heard plenty of horror stories about accidents that can happen from the use of retractable leashes, but many of them could also happen while using a regular leash.
Is there something I'm missing about the dangers?
No, not really. They're not much more dangerous than any long leash. They may be a little more prone to breaking, because the retraction mechanism is a bit more delicate than a bit of rope.
They're also usually thinner than a 'normal' lead, which means they're 'sharper' if something runs into them/gets clotheslined. I have very nearly come a cropper when cycling down a (cycle) path, when the owner is on one side, and the dog is sniffing something on the other side - the retractable leash was harder to see, and I have no doubt would have hurt quite a bit if I'd got it across my neck!
The major reason I don't use them though, is because of training - I don't want my dog to be bimbling around the road if she's on a leash, I want a clear distinction between 'walk beside me now' and 'go run free' off leash.
This seems to have helped with some anxiety issues she was suffering - one of the factors in anxiety is 'who is in charge' - a dog who feels she's in charge can get worked up and distressed when 'her pack' has wandered off.
I think there are many downsides to retractable leashes and not many upsides. The first thing that comes to mind is that you're not promoting good behavior in your dog. I want my dog to be right by my side when I have her on a leash. There is nothing I want her doing away from me, and that includes sniffing around. I've said in other posts that a dog has a wonderful sense of smell and they can smell most of the things from beside your leg as they can by walking over and sniffing them. If I don't care that my dog runs around and sniffs, I wait till I have good voice command and let them off leash.
You're also creating a two fold tripping hazard. I can't tell you how many people I've seen, go to step over one of these for whatever reason, only to have the dog run around and trip them onto their face. If you ever have to cross a line like this, use the sled dog method and step on the line with one foot. The other side is that your dog often gets yanked on at the same time, very roughly.
The more mechanisms that any object has, the more prone to failure it is, if you have a leash on, you don't want failure. The cord is also very thin and if it doesn't break or fray, then you run a very good risk of getting rope burn from a dog that pulls. The less surface area there is to a leash, the more pressure it puts on one point on your hand.
As a couple of real world examples, I was in the vets office a few months ago, getting my yearly shots for my two dogs. I had both of my dogs right at my feet. Something that never fails is that people want to let their dogs sniff my dogs at the vet. These dogs will never play with one another or socialize in any other way. Best case scenario is they're friendly. You're also running the risk of a dog fight for no good reason. I'd just finished asking a lady who was trying to do this to please pull her dog away, when I looked across the room and saw an elderly couple with a terrier mutt on a retractable leash. They sat and looked right at their dog as he ran across the isle, under a set of seats and attacked a dog that was lying there behaving. They laughed like he was playing. What upset me almost as much was that a nurse saw it and didn't say anything.
One more instance where having a retractable leash fail would be terrible is a situation with my aunt and her Pomeranian. She has him at the beach and she was lying out on the beach with her eyes closed and his regular leash wrapped around her wrist. She felt a pulling and looked up to see a german shepard with her dog in it's mouth, trying to pull him away. Luckily the owner tackled him and they got him out. He was fine after some stitches. He also had an owl try to carry him off once as well and dropped him when it hit the end of his tie out. Basically, he needs to quite giving off a snack vibe, but that's another problem.
So these are a few of the reasons I prefer a 1-2" wide and 6' long leash. For a little dog, you can go to the local supply store and buy a good bit of colored paracord, that's light weight and has a 550' test to it. You can make a nice light weight, but strong lead.
IMO their save use depends a lot on the dog's actual strength, weight and behavior. Never use such retractable leashes for strong or big dogs (Shepherds, Huskies, etc.).
This is mostly due to the strength of those leashes (or it's absence).
Normal leashes are typically sold in two or three variations for various dog weights, e.g. for those under or above 20 kg. But even the thinner leashes will typically be more robust and thicker than many retractable ones.
They may simply tear and/or their bearing could break.
Best case you'd be stuck with a leash that won't retract anymore. Worst case the leash might fly around and hurt you and/or the dog. Also not to forget the dog possibly escaping or running into a car (or whatever).
So in short I wouldn't use retractable leashes for any dog, unless it's really just something small such as a poodle or dachshund.
If you've got a strong and/or big dog and want to give it more freedom, look into buying a towrope/setline. You can use them for smaller breeds as well, just keep in mind that they've got some weight as well and the dog will have to pull it. Make sure to get a quality one though.
Those are typically 5-20 meters long (start with 10 meters if you're unsure) and they'll allow you to give your dog more or less freedom almost as easy as with a retractable line. They need some time to getting used to and they might not be as comfortable to use, but they're more flexible and without the downsides. Just make sure your dog doesn't surprise you just because he sees something interesting somewhere (but that's similar with other leashes as well).
