GrumpyMiddleAgedWoman
As I said in my pp, I've used a retractable lead on my dog for years - attached to a harness not, a collar, of course.
She's 10 years old and I have never in all that time caused injury to a passer-by, been tripped up or pulled over by my dog when we're using one, nor have I ever got myself or anyone else tangled up in one.
Perhaps that because I not an idiot and know how to use it without allowing these things to happen.
Used sensibly and properly they are extremely useful in certain circumstances.
Like absolutely anything, be it a retractable lead, an iron, or a car, if you use it in a stupid or dangerous way of course you are likely to cause injury.
People are killed by dangerous drivers all the time, nobody ever blames the car, why would they, it's the driver that's at fault.
In the same way, if a retractable lead causes injury it's because it's not being used properly or sensibly.
As tabulahrasa says: numpties are numpties - no matter what they use.