Gil,
Anecdotes aside, I think your analysis may be a little short on thoroughness. That being said, is my analysis shallow, too? Sure, but I think less so.
The press creates a human interest story that sells when it profiles a child prodigy that fails to live up to expectations. But is it a failure or are the expectations inappropriate? Perhaps we don't realize that in reading those stories, we adopt as accurate the high expectations.
I do not think there is a simple answer as to whether or not running competitively at a young age is dangerous emotionally or psychologically. I'm certainly not qualified from an academic standpoint to comment on that. But I do believe it depends alot on the individual.
For each child actor or young gymnast or tennis whiz that turns to drugs or other self-destructive behavior, I bet there are many more that simply find other interests that are not so antisocial in nature. These prodigies just channel their energy somewhere else, in a less dramatic fashion. There are many many stories that we just do not hear because they do not sell.
You state I may have peaked too early in life. I ran my best 1500 at age 24, my best 800 at age 21, my best 1/2 marathon at age 30, my best 10K at age 31. Those are about average ages for those events, so I'm not sure if I peaked too early, or if Briana and others like her will.
I do not think there is a really clear answer as to what is too young, and more importantly, too young for what? If one wants to be the next Geb, the next Decker? It is not a simple issue.