I'm not opposed at all. My child won't wear one so it's a moot issue in our household. I used to get a knee-jerk negative reaction to seeing them but having a "runner" has changed my mind. Yes, kids need to learn to hold hands, and I think in most day-to-day situations (e.g. at the Target, where mine loves to take off and run) you can teach this...but I also think in crowded places where it's hot and difficult to schlep 30 pounds around (Artscape comes to mind) a leash is a smart protective measure.

I used to joke with my wife that we would do this with our 1st. But now i find it just silly.

Do the "leashers" also crate their toddler at night?

I have never used a leash on my two boys, and they are high energy. They know to hold hands and stay with us.

I don't see anything wrong with it, as long as the "leash" is being used as a backup and used properly and gently. I used one with my first son - it was a stuffed bear that wrapped around him. He loved it and called it "Buckles." My son was very well behaved and listened when told to do something. But toddlers are impulsive. If he saw something that was incredibly interesting, he would break our hand-holding in a split second and bolt. That extra two feet of fuzzy tail prevented him from getting too far away before I could react. It also gave me peace of mind that no one could snatch him while I was distracted by something like paying at a cash register.
Unfortunately, I have seen some parents abuse the leash. They yank or drag their kids and treat them worse than most people would treat a dog.

As I'm writing this, my kids are playing dog. My 6 year old is using an actual dog leash to "walk" his sister. Of course, she's crawling down the hall on all fours, barking, and I'm pretty sure she just took an imaginary pee on an imaginary tree. I know it's not the same, but still thought it was funny,

I never used a leash, but I think if other people want to, it's their business. A busy airport or other place is not the time to teach a child a lesson about staying close. The people who are so against leashes are probably also the ones who would complain about kids running in Target and then ask management to ban them from the building.

we never used a leash but I'm not opposed to them, well I was until 5 years ago we took our 3 year old son to Disney World, the sheer size of that place and the thought of losing him in that crowd suddenly made it clear to me why you would want to use a leash. Luckily he was a clingy kind of kid, back then, so he never got too far way.

That's not say I don't snicker when I someone walking the dog with a baby in a stroller and a toddler on a leash too.

Most people would agree in parenting you really need to choose your battles. In my opinion this battle is worth fighting. It could save a child's life. I never used leashes and always chuckled when I saw another child attached to one. I always thought to myself "That poor child. No one has the attention span to hold his hand and keep him safe." I have had three toddlers I had to watch over and keep safe in places filled with people and I trained them all from the time they could walk steady to hold hands with Mom and each other. I don't mean to be hard on Mom's who use leashes, but an ounce of prevention is worth a pound of cure.