I have received many great responses in this post, and they are very helpful in learning to understand the thinking of the W.T. organization. Thanks so much.
In summary, from what I gather here, here's many of the reasons j.w.'s leave the cult :
Light always changing, doctrinal errors.
No love, or support from elders, family.
Lost spirituallity, logic.
Forums, books, especially "C of C".
Changing Jesus' role.
Too strict on children.
Are there any other reasons anyone can think of ?