This is literally a "pet" peeve - The extendable leashes that people use for their dogs. What is the point of a leash if it extends for a half of a mile? Are you really taking your dog for a walk? I don't know if it qualifies when, technically, you could stand on your front porch while your dog walks itself around the block on it's extendable leash.
One of the reasons that this type of apparatus peeves me is that I find it irritating that a dog can be sniffing my buns and generally invading my own private space while his owner stands on the other side of the street holding his "leash". The extendable leash is sort of the antithesis of the child leash, which I have peeved about before. The dog needs a leash. It is only polite. Control it. Put something on your pet that won't allow him to extend beyond your line of vision or the beyond the line of reason.
P.S. While searching for a photo to accompany this peeve, I just found out that this type of leash is, in fact, quite dangerous for the animal at the end of it...so, HA, an even more substantial reason not to use one!!