I solo thruhiked back in 2000 when I was 16, turned 17 on the trail. It was an excellent reason to drop out of school for a semester; I certainly learned more on the trail than I would have in the classroom. It takes a certain amount of maturity that perhaps some people don’t have at that age, but the simple fact that you’re here doing research says that you’re probably ready.
As far as safety goes, the trail, in general, is a very safe place. Just be very aware of your surroundings. Over the years I’ve met a few crazy whack job hikers that caused me to put some miles between us, but you usually have nothing to worry about from other hikers. The places to really be on your guard are near road crossings, in towns, and while hitching. You can always try and hitch with another person, if that makes you fell more comfortable. And remember that you can always refuse a ride from someone; if they pull over and look nuts, just say no thanks and start walking away. That being said, I sure do love hitchhiking, you get to meet some interesting people.
Backdraft