Hello Shannon,
Even in the small rural town where I lived for 13 years I met homeless teens.  Some became extended family, some came to visit at dinner time, some came home with my kids and stayed over night now and then.  They all had something in common.  They had been either forecefully emancipated by their parent(s) or they left for their own safety and well being.  Back in the day as they say, it was not uncommon for a young person to simply leave home after graduating high school.  They were often dependent upon another family member to help them along as they found a job and tried their wings.  Eventually most found a decent job or joined the service.  Then came the "hang on" generation.  They were expected to continue their education and in return got a few more years at home or living expenses at college.  Today the competition is fierce, the economy may prohibit college for a teen and moral may be so low that a kid will leave home to avoid over burdening the family, or the tension grows until they leave on less than comforatable terms. 
No matter how it happens, it happens.  In every community.  I have witnessed the "what homeless teens?" phenomenon too.  They learn how to fly low to avoid trouble.  Fact is that there are many young people who are out there in unsafe conditions over night, with no income and what food they can find.
These kids are our future too.  We have all seen a movie or read a story about how now and then a kid gone wrong makes good.  What you don't hear much about is a young person who is living in a car and trying to stay in school.  Or a kid who has hit that 20 year mark and is no longer considered a kid who is still not "socially engaged".  Is there a magic number where a kid becomes enlightened and all burndens are lifted?  Not without a little support and coaching.  And l won't even mention the foster care system right now!  How do we bring these kids into the fold?  How do we help them help themselves?  One safe place at a time. 
I yearn for a national program to help get a lot of these kids into a safe co-housing situation in their own community. 
I have been working on such a model for years now.  I see that one or two do exist out there.  That's great, but how do we make it a nation wide effort?  My model includes a component that is very relative to today's needs.  Part of the plan is to not only introduce how to live more lightly and responsibly but also to get these young people trained to become part of the alternative energy movement.  More to come if you would like to hear.
Lynda