I know two people who've broken a Kindle, and they were both tweens. And one of them is definitely irresponsible with her things -- her parents buy her so much that she doesn't value and take care of expensive toys. I'd guess that teens might be more likely than adults to toss a Kindle into a bookbag.
On the other hand, my Kindle's an older model that's no longer available, and it's in perfect condition because it's literally always either in my hand or packed away in its protective case. And I have a friend my age whose brand-new Kindle "just wasn't quite right" -- it'd hang up for 5 minutes, then start working again -- and she sent it back to
Amazon on Day 2 of ownership; they exchanged it without any trouble. Aside from her, I haven't known an adult who's had a problem, and I'm sure she had the bad luck to get a defective one.
If I end up buying these for my daugthers for Christmas, I think I will get the insurance for them -- though I probably woudln't do it for myself. I think it might be most important for my soon-to-be-a-college-student daughter. Living in a dorm room, things on her desk could easily be subjected to food, drink, friends -- it'd be very easy for something bad to happen to her machine. Hmmm . . . my Kindle cord is really cool: It's a wall plug-in, but if you pull off the "prongs thing" it's a USB underneath. Sounds like they may've developed a cheaper model? I'd want to know for certain before ordering.
Personally, my favorite charging method is my little docking station. It sits in the bay window in my bedroom behind a curtain, and it's super-convenient.