Everyone wants to give their dog as much freedom as possible and still keep them safe, right? It would stand to reason, then, that a long leash which is quickly retractable, would be the best thing out there. These leashes can be useful and helpful, but more often than not, they're a nuisance at best, and downright dangerous at worst.
Retractable leashes are great if you've got your dog in a big open field and you're letting your dog be a dog: sniffing, gamboling across the field, pouncing, playing. And that's about the only place and time that retractable leashes are good.
You can lose a finger, get a rope burn or break your dog's leg. These leashes are NOT good near roads, near other dogs, in pet supply stores, in training class, in downtown areas, or in doggie parks. Used in these locations, they actually hinder you and your dog.
Retractable leashes can actually teach your dog to pull on the leash. Because there's always tension on the leash, the collar is always tight. If the dog knows that to go anywhere his collar must be tight, you'll never convince him to not pull even when he's on his regular leash.
If you're headed anywhere other than a wide-open field, use a standard 4- or 6-foot leash. I like plain cotton web leashes – they come in varying lengths: 20, 30, even 50 feet. They don't retract which means there's less chance of me losing a finger, and there's never tension on the leash.