I don't think the world is inherently more dangerous than it was 10,20,30 years ago, we're just more aware of the bad stuff now than we were before. We also don't put as much emphasis on teaching kids practical world skills as we once did. I see so many kids today (kids of friends, neighbors etc) that are over-protected, shelted to the point where they can't actually deal with something going wrong.
The prevailing wisdom now seems to be that if you're under 18, you're incapable of doing for yourself, or you're somehow intensely vulnerable and some predator is going to sweep out of the shadows any second to snatch you up! It's part of the whole "My angel would never do anything wrong!" and "You can't give little Johnny a bad grade! He tried really hard" attitude that's been growing and growing for years now.
Kids are a lot tougher and more resourceful than most people give them credit for. Treating them like a china doll that you keep under lock and key all the time isn't going to help them at all when they're suddenly out in the real world and have to deal with danger and mean people for the first time in their lives.