John Gee has post two important blogs on the question of why youth leave the LDS Church (and religion in general). Unlike much opinion, his analysis is based on hard statistical data from the National Survey of Youth and Religion.
http://fornspollfira.blogspot.com/2014/12/why-do-they-leave.html
http://fornspollfira.blogspot.com/2015/01/why-do-they-leave-ii.html
He promises a third post will be forthcoming.