A couple of friends and I have taken up hiking here in South Africa and they're pretty geared up with their ankle guards, and extreme hiking shoes and what not. They've got their hiking underwear and whatever else they feel they need.
I've always always been opposed to heavy bulky shoes, and always wear minimal stuff. Heck I even said a prayer after ZemGear shut down their operation, so sad so sad.
I hike fine with my minimal footwear. I'm extremely light on my feet, so my toes do not bump into anything, and I tread lightly with quite a bit of agility, so I move like a ninja.
The only thing is, my feet are pounding after a hike. As in muscle-pounding. It's like when you do too many wrist-curls, but on my feet. Personally this is a feeling I welcome, and love. And my feet heal within a couple of hours after the hike, so it doesn't bother me.
But is it unhealthy in the long-run? (I promise, I did not intend that pun.)
EDIT: As requested, I don't hike with just my sneakers or anything. I specifically purchased a thick-soled aqua sock so that I could enjoy the many waterfalls we encounter on our hikes.